The strange case of Baroness de Stempel: How the death of an eccentric architect revealed a web of murder, fraud and intrigue

The ancient church of St Edward sits on a hillside, overlooking the scattered houses of Hopton Castle, an isolated Shropshire hamlet, which lies just where the lush green meadows of England merge with the brown hills of Wales. The background sounds are of sheep bleating, water running and a breeze that rustles through the pines across the valley, bringing a scent of far-off wilder places to the west.

To get to the churchyard, you park on the grass verge, cross a rickety bridge over the stream, and go through two aged wooden gates, before entering the churchyard. There, on the left, near a stone wall, is a striking black granite headstone. Its border is a series of engraved images: some books, a few scrolls, a typewriter and an architect's compass. At the top, there is another, of a mansion. The inscription reads:

Simon Dale
Architect and Scholar.
Who with his wife saved Heath House from demolition.
17 June 1919 – 11/12 September 1987.
REQUIESCAT IN PACE.

The casual visitor might think this headstone poses more questions than it answers. Who was this architect and scholar? What is Heath House? Why is the date of death uncertain? And who was, or is, the wife, whose name is curiously absent?

In 2007, William Wilberforce, the Victorian politician whose name will forever be associated with the abolition of slavery, has been justly celebrated, not least in the film Amazing Grace and a new biography by William Hague, because this year marks the 200th anniversary of the date Parliament approved his bill to ban the transport of slaves. This year, there has been one other significant anniversary associated with the illustrious Wilberforce name: an event much less celebrated, although it might make a better film than Amazing Grace. It is the story behind the headstone.

Simon Dale, an architect who was blind and whose scholarship was deeply eccentric, was married to Susan Wilberforce – the unnamed "wife" of the headstone – the great-great-grand-daughter of William Wilberforce. Twenty years ago next month, one sunny Sunday afternoon in September, he was found battered to death in the kitchen of Heath House, the crumbling mansion that they, as newlyweds, had saved from demolition and turned into their family home, but which, after their divorce, became the subject of an acrimonious dispute. And Susan Wilberforce was charged with the murder of her ex-husband, although she was cleared at trial. Hence the absence of her name. Two decades on, the murderer is still at large, the police file still open.

That is not all. While investigating the murder, detectives stumbled across another crime: Susan, together with her second husband, Baron Michael de Stempel, and two of her five children, had defrauded Margaret, Lady Illingworth, her elderly and senile aunt, who had once organised Susan's debutante party, of an estimated £1m. Susan pleaded guilty to fraud; Michael and two of her children, Marcus and Sophia, both in their mid-twenties, were found guilty. The judge called Susan a "malign and appalling influence" on her offspring.

While entertaining to outsiders, the affair was deeply embarrassing to the Wilberforce family, a dynasty created by the abolitionist's four sons that has given centuries of unstinting service to the nation's institutions, reinforcing their reputation for integrity, without ever accumulating the serious wealth of other such families. Susan's great-uncle was Lord Wilberforce, a Law Lord, who died in 2003, while her brother John, who died in 2001, was the British High Commissioner in Cyprus. Both gave evidence for the Crown at the fraud trial.

Unanswered questions remain. Why did the Wilberforce clan not report the stripping of Lady Illingworth's assets? What happened to the £12m-worth of gold bars possibly in Lady Illingworth's possession? Who did kill Simon Dale? Why were crucial witnesses not called? For answers, one must look further than the graveyard at St Edward.

Susan Wilberforce, then 23, met and married Simon Dale in London in 1957. Fifteen years her senior, he was a cultivated man from a middle-class Oxford family who worked on restoring country homes; she was a young woman about town. Her upbringing had been one of large chilly houses, strict discipline, finishing school in Paris and rather distant relatives. Her father, Lt Col William Wilberforce, great-grandson of the abolitionist, died in the Second World War; her mother remarried and was a marginal presence in her life – hence the involvement of her father's sister, Lady Illingworth.

Susan provided Dale with, in the words of his friend the late Christopher Hurst, a publisher, "entry to the class he had courted professionally", and he brought a solid, male presence to what had been a rather rootless life. Pursuing their ambition to restore a country house, they purchased Heath House in 1959, paying £2,000 of her money for a semi-derelict shell its owners had been about to demolish. Built in 1620 for a local squire, the house sits squarely amid the trees, facing the hills to the south-west, in what is still a rural, sparsely populated area, a few miles west of Ludlow. While it is a peaceful, beautiful region, almost entirely by-passed by tourism and motorways, even its strongest admirers admit Heath House was isolated and gloomy. "My heart sank at what they were contemplating," said Hurst.

The 1960s passed them by as the couple remained cocooned in Heath House, spending all their money on schooling their five children and renovating the house.

Contact with neighbours was minimal, partly because of their preoccupations, partly because few locals had much in common with them. But it was also because Susan, like many of the Wilberforces, was shy and reticent, characteristics reinforced by her upbringing. What others might see as aloofness and disdain is the Wilberforce way.

There were few distractions, apart from family visitors. Curiously, in view of later events, in November 1968, a local GP, Dr Alan Beach, was lured to the house by the husband of a patient, unhappy about the late diagnosis of cancer in his wife; the doctor was shot dead in his car at the top of the drive. The incident had nothing to do with the Dales, but seemed of a piece with the aura of the place.

By the end of the 1960s, the marriage had broken down. Dale's eyesight was failing, his outside work had dried up and the idea of his wife getting a job was unfeasible. There were arguments and she later claimed he suffered .........  violent moods, frustrated by his condition. They lived in different parts of the house, with the children mostly away at a succession of schools. They divorced in 1972 and she left a year later. As a condition of the settlement, Heath House was to be sold and the profits divided between them.

It never was. For the next 15 years, a combination of unstable house prices, a scarcity of buyers and Dale's refusal to move frustrated any sale. Susan, relying on family handouts, moved around before settling at Forresters Hall, a grandly named but small roadside cottage in f Docklow, near Leominster; the younger children were mostly with her, bonding into an insular unit, but they also visited their father. The correspondence between the solicitors mounted up, but both parties were too impoverished to pursue the matter in court.

Meanwhile, Dale lived mainly in the kitchen, sleeping upstairs in a four-poster bed. The rest of the house was half-empty, full of dusty furniture and discarded children's toys; one room contained just two rocking horses. "Like the Marie Celeste," said Hurst. Dale's determination to stay was founded mainly on a belief, based on his excavations and researches, that Heath House was an important historic site: he claimed variously it was the location of Camelot, the centre of a Pagan cult and the lost city of the ancient Armenians. "What I appear to have found are streets, 40 feet wide and 200 yards long... shops, houses, that sort of thing," he told the Manchester Evening News in the late 1970s. He was writing two books about the remains and wanted the site preserved, with himself as curator.

The scepticism of professional archaeologists only reinforced his belief that the establishment was conspiring against him. His friends and children took it with a pinch of salt: "Simon was fine if you kept him off the old Armenians," remembers Veronica Garmen, one of a group of locals who took pity on him in the mid-1980s. "He had no money, of course, and I used to have to darn his only sweater.

"And..." she says, still conscious of the rumours, "Simon was not violent. Never. He was a big gentle man. Neither was he a recluse – he was just cut off in that big old house and a bit lonely. We used to go around and cheer him up."

All his friends and those who used to read for him and help in his researches have only fond memories. "He was a reasonable chap, but eccentric, a five-star eccentric," said Bill Harper, a neighbour. He saw him frequently: a tall, balding man, who would stride, despite near total blindness, across the fields to Leintwardine, the nearest village, where he would buy his regulation small white loaf and cheese from the shop. He would make each loaf last precisely two and a half days.

While Dale hung on, the extraordinary figure of Baron Michael Victor Jossif de Stempel had re-entered the life of his ex-wife. From a wealthy Russian émigré family, holders of an ancient Latvian title, De Stempel, who describes himself as an economist, may in fact never have done a proper day's work in his life. This is a man whose own barrister said a jury might consider him to be a "monumental snob", a "congenital liar" and "a man without courage".

Susan first met him in the rooms of her brother John, at Oxford, shortly before he, Michael, was sent down. He became a man about town, spending his nights at the Ritz – they pleased him by addressing him as " Monsieur le Baron" – and attending parties such as Susan's coming-out ball. He was obsessed with ancient families: the intense, black-eyed Susan Wilberforce, proud that she could date her ancestry back to the 12th century, fascinated him. They began a relationship shortly afterwards, although she rejected his marriage proposals because of his unreliability. The affair continued, on and off, for several years; Dale came along when Michael was away in South America. Michael married the first of his three wives shortly afterwards.

Susan, though, was not forgotten. "It was a mutual fascination, but Michael undeniably weakened her," as one of her children later said. They never lost touch and Michael visited Heath House with both of his first two wives. He rather liked it and at one point began having his post directed there.

In 1982, with both divorced, Michael began to visit Susan at Docklow. The relationship resumed – sometimes they would spend the day in bed, studying Debretts and the Almanach de Gotha – and he helped Susan out financially, not least in the defrauding of Lady Illingworth.

She, the widow of Lord Illingworth of Denton, a former Postmaster General from a prosperous Yorkshire wool family, had lived the life of a Mayfair socialite at her home in London's Grosvenor Square. Now in her early eighties, living in a mansion flat and suffering from senile dementia, Lady Illingworth was brought "for a holiday" to Docklow in February 1984 by Susan's daughter Sophia, who had been staying with her while working as a temporary secretary. Police believe the fraud was not planned in advance, but grew out of Susan's belief that after the poverty of the past decade, she was entitled to family money. Her brother John, resident in the Wilberforce family home in Markington, in Yorkshire, was the main beneficiary of their mother's will, while Susan may have known she was excluded from Lady Illingworth's, again in John's favour. And, anyway, were not the Illingworths just a bit nouveau?

Within a couple of weeks of the arrival of Aunt Puss, as they called her, her bank accounts had been plundered using a series of forged signatures, her shares were sold and, as insurance, a new will forged, leaving the bulk of her possessions to Susan. Also using forged authorities, all her furniture, antiques, jewellery, paintings and other valuables were taken from her London flat, out of storage and from bank vaults and sold at auctions. They got away with around £1m, spent mostly on cars, holidays and a flat in Spain. After nine months, Lady Illingworth was dumped in a Hereford nursing home, because, Susan told social workers, they could not cope with her senility.

In late 1984, Susan and Michael finally married in St Helier, Jersey, a trip funded by the sale of £13,000-worth of Aunt Puss's jewellery. It lasted barely a year. They found it impossible to live together. Michael refused to commit himself and became involved with another woman. He would later claim he had only been "technically married" to Susan, who was still, he said, "fiscally married" to Simon. Now it was Susan's turn to beg, writing imploring, melodramatic letters: "My heart aches at the thought of being apart from you." She even claimed to be dying of cancer.

When Aunt Puss herself died at the end of 1986, she was cremated in virtual secrecy at Hereford, with none of the other Wilberforces, who had only been dimly aware of her whereabouts, told until later; the cremation directly contravened the request in her earlier will that she be buried alongside her husband, at the Illingworth family tomb in Bradford. The obituaries suggested she had spent her last days in a suite in Claridges. Her real fate remained unknown to the wider world until Simon Dale was murdered.

On 13 September 1987, Simon Dale's body was found by Giselle Wall, who had helped with his research, lying in a pool of blood in the kitchen, toad-in-the-hole was still cooking in the oven. He had been battered around the head with a hard, narrow instrument.

Police suspicion immediately fell on Susan after they learnt that she, together with Marcus and Sophia, had been spending much time there improving the house's exterior and grounds in the expectation that renewed legal efforts to evict Simon would bear fruit. She admitted breaking in sometimes to take furniture she considered hers. All this had led to angry verbal confrontations with Simon – who felt himself under siege – and visitors to the house. Susan, Sophia and Marcus were charged with his murder, although proceedings against the children were halted after a few weeks. All three, plus Michael, were charged with the fraud, discovered during routine financial checks.

Susan treated the police with contempt: "You would have been proud of me," she wrote to Michael, "if you had heard the lectures I gave all those little men about the ancient nobility of your family and mine." The little men, in turn,

were astounded at the lack of emotional response when they broke the news of Dale's death to those at Docklow. Susan refused to answer questions, or gave dismissive denials.

It was a short, dramatic murder trial at Worcester. The Crown had no direct evidence other than accounts from visitors to Heath House who had seen her lurking in the grounds on the previous Friday evening. A recently cleaned crowbar found in a cottage used by the trio was put forward as the murder weapon, although there were no traces of blood. The highlight of the trial was her performance during a two-day-long interrogation by Anthony Palmer QC, one of the country's best inquisitors, who was treated like a dim retainer for even suggesting her mounting anger with Dale had turned into violence. "I wish you would get into your head, Mr Palmer," she announced loftily, "that I was not angry with Simon." Another accusation was dismissed with: "Bollocks, Mr Palmer!" Ian Bullock, the detective superintendent in charge of the murder inquiry, remembers her disarming composure: "At the end of a long day in the witness box, it was she who looked down at me and said, 'You do look tired, Mr Bullock' ." Most observers felt she had won on points – the jury clearly agreed.

But Susan remained in custody for the fraud, changing her plea to guilty shortly before the trial started. At those proceedings, in Birmingham in early 1990, the jury rejected Marcus and Sophia's claim that they had simply been unwitting tools in the defrauding of Aunt Puss. The jury also rejected Michael's protestations of being "merely a porter"; his assistance in the intricacies of banking and wills had been fundamental.

Afterwards, he said: "It was about what I would have expected from a working-class jury." Susan got seven years, Michael four, Marcus 18 months and Sophia 30 months; police believed the judge correctly apportioned sentences to their respective involvement in the plot. Throughout, no one mentioned the gold bars.

The gold bars were just one of several mysteries around the case which have never been resolved. Police were told by one of the men who moved Lady Illingworth's property into storage when she left Grosvenor Square in the late 1960s that he had seen a number of gold bars in the basement, apparently sent for safekeeping by a French family who perished in the Second World War. They were shifted to the local NatWest bank vault, the one plundered years later during the fraud. But no gold bars were itemised on the bank's own inventory. There was a reference to "Boxes (very heavy)", but the police could find no evidence they existed. But someone clearly believed they were real. A month into their prison sentences, all four received writs from solicitors acting on behalf of Lady Illingworth's estate demanding the return of "30 gold bars, each 18 inches long, total value £12m". All thought it laughable; the police privately agreed: "If they had got that much, they would not have stayed in that little rented cottage in Docklow," said one source. f Even so, the writs prompted a police dig in the grounds of Heath House. Nothing was ever found by the trustees in bankruptcy.

I got to know Susan and three of her children when researching a book on the case, published in 1991. Susan, whom I interviewed in prison and corresponded with, was, as billed, a disquieting combination of aristocratic aloofness and impeccable manners, coupled with an ability to brush aside uncomfortable questions as if the whole thing was simply too distasteful. She told me she refused the police offer of a plea to manslaughter on the murder charge. "I would rather have gone to prison than admit to something I did not do." Apart from a "she was very happy", questions about Aunt Puss were sidestepped. But one thing she was clear about: her pedigree. "I know who I am. The one thing money can't buy is breeding, don't you agree?" she wrote. There was no irony.

After her release she was penniless, spending her time with lawyers and accountants attempting to sort out the tangled mess of wills, bank accounts and competing writs she caused. One accountant recalled the same air of denial: "She sat, handbag on her lap, very polite, a fixed expression, as if we were having tea and scones. When I pointed out that she had taken all her aunt's money, she simply gave me one of those 'if looks could kill looks...'. " Several publishers were offered her version of the affair but none was prepared to pay.

Predictably, the relationship with Michael resumed, although they never lived together. She lived in Wales and London, but then when the relationship foundered again a few years ago, moved to Hastings, where she still is. Now in her early seventies, she has recently suffered heart problems. Last year, she sent a card to "Darling Michael" on his 75th birthday with the message: "Hurry up, it will soon be too late".

The Baron mostly stays with his second wife, Francesca Tesi, in a small terraced house in Acton, west London. Their son, Alexander, died in 2003. The three children from his first marriage have enjoyed success: one daughter, Sophie, an artist and a former model for Lucien Freud, is married to the actor Ian Holm; Tatiana, his other daughter, is also a painter; his son, Andrew, is a doctor.

Marcus and Sophia Wilberforce, when I met them, seemed much younger than the average late-twentysomething, despite their resolutely old-fashioned dress sense and introverted manners. Sophia received psychiatric treatment during the trial and never read a word of the official papers. During long sessions with their lawyers she would offer to make tea. When she confronted her mother about the enormity of what had occurred, Susan simply said: " Don't be a bore."

"We were used," Marcus told me, eventually, very quietly. One dark winter's night he showed me around Heath House's dusty rooms; we chatted around the table where his father ate and worked, in the kitchen where he lived and died. Asleep on the table was Oats, the cat they bought for Aunt Puss.

Both are now in their forties. Sophia still works as a temporary secretary in London; Marcus married and lives in Scotland, where he is a building surveyor. Their current relationship with their mother, while unclear, seems unlikely to be close.

All four have repaid their debt to society. None has acted as if they have access to £12m. Mike Cowley, the officer who headed the fraud part of the inquiry and is now a CPS solicitor, said: "Anything which now remains is a matter for their consciences."

Of the other children, Sebastian, the second oldest, the one closest to his father, who shares the same eye condition, is a solicitor and expert on charity law. He lives in New Zealand, with his wife and family. I also got to know Sebastian during my researches: a decent, diffident man, shattered by the events and concerned about the reputation of his father, whose headstone he commissioned. I telephoned to ask whether the children thought West Mercia police should use the 20th anniversary of the murder to launch a fresh appeal for witnesses? "I'm sorry," he said. "I've nothing to say. And that goes for all of us."

Which was the official Wilberforce line all along. The family closed ranks, resisting questions as to why there was apparently only minimal interest in what Aunt Puss was doing for the period of almost three years between her move to Docklow and her death; only Yvette, wife of Lord Wilberforce, told the trial she "regretted" never trying to find why her letters to Aunt Puss at Docklow went unanswered. Police believed they would never have discovered the fraud, if it had not been for the murder.

If Susan didn't kill Simon, who did? Inevitably, there were rumours of hit men and disputes with local people, not called to give evidence. "I never believed the hit-man theory, but then one policeman said if you went into a certain pub in Leominster, there were people who might do such a thing," said Veronica Garman. Then there was a mysterious hitch-hiker, seen on the road outside over the weekend of his death, but never traced. Crucially, as the headstone indicated, police never established the time of death: the intense heat from the cooker distorted the rigor mortis process. Most evidence pointed towards Simon being killed on the Friday night – the line taken by the Crown at the trial. But according to Bill Harper, as dependable a witness as could be, Dale was alive on the Saturday. "I am absolutely certain I saw him striding across the fields on Saturday lunchtime, 80 yards away, carrying shopping home from Leintwardine." He told me: "I wasn't treated very pleasantly by the police, because it did not suit their case that he died on Friday. But it was him, I'd stake my last penny on it." Neither Harper, nor the two people with him, was called to give evidence. These issues may or may not be significant, but suggest the evidence was nowhere near as straightforward as it seemed. Despite scientific advances which have solved many "cold cases", West Mercia Police has no plans to revisit the Dale file "in the near future". Or in the words of another officer from the inquiry: "The case against Susan was put to a jury and they didn't agree."

The deepest irony is that Susan could never return to Heath House, the place that consumed her money and energies, helped destroy her marriage, break up her family and give two of her children criminal records. It was sold at auction, to pay her creditors, for £272,000 in 1993. In 2000, it was bought by Rupert Lywood, a City figure, for £1.5m. Today, it must be worth several million pounds. To get there, you still take a sharp left off the main road, past the gate where Dr Beach died, and plunge down a driveway through a copse. But now the grounds, once wild and unkempt, have been landscaped.

Of the 30 gold bars, there is still no sign. The house has been extensively renovated, although it is currently empty, and all traces of the kitchen where Simon Dale lived, worked and died, are long gone, along with the dusty upstairs rooms, the rocking horses, the broken bits of furniture. The brickwork and the exterior have been cleaned, although the original massive oak door remains, as does the gap in the hedge by the kitchen door, the one Giselle Wall could not open because Dale's bloodied body lay on the other side. There is a swimming pool, and several outbuildings have been converted into rented cottages.

"Gosh!" exclaims a young woman from one of the cottages, who says her name is Heather, when I tell her it is the scene of not one, but two murders, the latter still unsolved. She is genuinely surprised. "We've been here a couple of months and no one told us. And my partner's a police officer over the border in Radnor – he will be fascinated." We joke about how he might solve it, one day. She says she came up from Devon to be with him. "I love it here," she says, sweeping her arms wide to show me across the lush green lawn, the pleasant shrubberies and tall, mature trees. "It is such a peaceful place. We're very happy here." Good luck to them, one feels.

It is a warm, if showery, summer's day. But as we talk, that sudden cool breeze passes through the trees again, as if there was something unsettling over the horizon.