William Shand Kydd: Businessman, bon viveur and the friend to whom Lord Lucan turned after murdering his children's nanny

He claimed that he was deterred from writing an autobiography by the thought of all the husbands who would be after him

Shand Kydd and his wife Christine in 1971; she appeared to tolerate his extramarital activities (Getty)

Bill Shand Kydd embraced the trappings of his privileged upbringing, enjoying life as a bon viveur and becoming a businessman, an adrenaline-fuelled sportsman, womaniser, gambler, successful jockey and racehorse breeder. Even a fall which left him paralysed from the neck down could not temper his reckless lifestyle, and he went on to raise millions for charity.

However, he was perhaps best known for his association with two of the aristocracy's most fascinating and enduring characters – Lord Lucan, and Diana, Princess of Wales, whom he described as "a cracking bird, much better than she looks in pictures".

Shand Kydd and his wife Christina had introduced Christina's sister Veronica to Lord Lucan and the couple married; he was a trusted friend of Lucan. On 7 November 1974 the Lucans' nanny Sandra Rivett was murdered in the basement of their home at 46 Lower Belgrave Street in central London. Lucan then drove to the home of his friends Ian and Susan Maxwell-Scott in Uckfield, East Sussex, from where he wrote two letters to Shand Kydd. It is understood he also tried to telephone him, but Shand Kydd's bedside phone had been switched off – "and when the girl answered the phone downstairs she thought I wasn't in." Shand Kydd felt certain that if they had spoken he could have convinced Lucan to hand himself in.

That night Lucan disappeared and was not heard of again, although Shand Kydd, who viewed him as "not one of my greatest friends, but I liked him," made a personal appeal to him on News at Ten to come forward. "I don't believe he killed the nanny," Shand Kydd said. "There was blood on his hands because he was wiping it off his wife's head. If he'd murdered the nanny, he would have been smothered in blood because it was all over the walls."

Lucan's letters, written on blood-stained paper, described how he had seen an intruder struggling with his wife, and went on to ask the Shand Kydds to look after his three children: "I am going to lie doggo for a while and would like them to live with you." They eventually did so in 1982, after their mother had a breakdown. George Bingham, Lucan's heir, would later describe Shand Kydd as a "perfect role model". The second letter was a request that proceeds from a sale of family silver be used to clear Lucan's overdraft and debts.

At the inquest in 1975 Lucan was named as Rivett's murderer; his car had been found abandoned in Newhaven, its interior stained with blood and its boot containing a piece of bandaged lead pipe. Despite sporadic alleged sightings all over the world, Shand Kydd never saw Lucan again and never agreed with the assertions of his guilt; he believed he probably took his own life shortly after his disappearance.

Shand Kydd also had another famous association. For 19 years his older half-brother Peter was married to Princess Diana's mother, Frances, after her divorce from Earl Spencer, although he was not close to his step-niece.

Born in 1937, William Shand Kydd was the son of the wallpaper tycoon Norman Shand Kydd and his second wife, Freda. He was educated at Stowe and completed his National Service in the Royal Horse Guards before marrying Christina Duncan in 1963.

He admitted that this did little to stop his roving eye. He once claimed that he was deterred from writing an autobiography by the thought of all the husbands who would be after him. The secret of his success with women, he said, was "perseverance and gratitude". He clearly inspired extraordinary devotion in his lovers, while his wife appeared to have tolerated his transgressions, although they did have a short separation.

Shand Kydd joined the family wallpaper and Polyfilla business, while setting up homes in Chester Terrace, by Regent's Park, and a renovated farmhouse near Leighton Buzzard. He left the business soon after to become a property developer, invest in start-up companies and farm his Buckinghamshire estate.

At the same time he enjoyed the high life and adrenaline-fuelled sports; he did the Cresta Run at St Moritz, where he first met Lucan, raced power boats, again with Lucan, and became an amateur jockey; he rode 45 winners under rules and more than 120 in point-to-point winners. He rode the 1966 Grand National – unseated at the 25th fence on the 50-1 shot Dorimont - and won the 1973 National Hunt Chase at the Cheltenham Festival on Foreman.

A dedicated gambler, he once won and quickly lost £70,000 playing Chemin de fer at the Clermont Club. The experience induced him to give up gambling.

In 1995 his horse Captain Pike fell on him, leaving him with two broken vertebrae and paralysed from the neck down. "Girlfriends came in droves to the hospital," he said. Ever the optimist, he remained upbeat, saying, "I've joked my way through my life and my memories are very sustaining."

Unperturbed by his disability, Shand Kydd set about fundraising for Spinal Research; he took part in a 12,000ft skydive strapped to an instructor, complete with respirator, raising more than £1m. "I've always liked new challenges and doing things I'm told are impossible," he said. "That's been my philosophy all my life."

William Shand Kydd, businessman, jockey and racehorse owner: born 12 May 1937; married Christina Duncan 1963 (two children); died 27 December 2014.