As a boy, John Kingston listened with fascination to his Polish stepfather's stories of wartime horror and cruelty.Then it dawned on him that these might not be the tales of a witness, but of a participant. Now he is campaigning to get his child hood hero prosecuted as a war criminal. Stephen Ward reports. Portrait by Mike Abrahams

When I was a boy, my father used to demonstrate how they would shoot people with a pistol. He would mime holding a gun to the back of his head, the place at the top of the spine."

For seven years, John Kingston has been obsessed by finding out what his stepfather did in the War. He has read every book he can find on the area of eastern Europe where his stepfather came from. He has spent weeks in libraries researching births, marriages and deaths. He has been to see houses and camps deserted before he was born. He has burrowed in old newspaper files for clues, and bombarded consulates and embassies with requests for information. He even sent a dossier to Scotland Yard, because he has become convinced that the man who as a child he regarded as a hero may have been a war criminal.

John Kingston, 51, lives behind a very high and thick beech hedge in a council house on the outskirts of Holmfirth, on the edge of the Yorkshire moors. They film Last of the Summer Wine in the countryside all around, but use bright lighting even in June and July to make it less bleak. His house is armed with security lights and burglar alarms, partly to keep out prying neighbours who have heard about his obsession and mistakenly think of him as a Nazi. But the defences are also against a less tangible and more sinister threat: since he never knows whose past his research may uncover, there may be mysterious expatriate organisations still actively protecting their secrets.

Kingston looks and sounds like a North Country farmer, stopping to think and chew over the implications to himself before answering a question. He doesn't seem paranoid, although he is certainly driven, pursuing his quest with more than a strictly rational purpose, but not crazily and wildly.

John Kingston was a war baby, born to a 16-year-old single mother in Birmingham. She had met his father at his anti-aircraft base, but by the time the baby was born he was away in the Army on the Rhine. The couple married during one of the soldier's home leaves. They also had a daughter, but after the War, as soon as divorce became easier, they split up. As far as John was concerned, he had never really had a father. "When I saw him," John remembers, "he was just a stranger. He seemed a rather distant figure, he preferred to be with his mates."

The boy drifted emotionally for a while, a latchkey child in a bombed- out city. Then, when he was nine, his mother met Stasic Chrzanowski, and the tall, powerful, domineering, hot-tempered Pole moved into his home and took over his life.

"When my mother first introduced us, I was looking for a father, and he was looking for a ready-made family and a son." John used to sit and listen spellbound to his new father's stories, hero-worshipping all the more because for so long there had been no one there at all to look up to. His new father's stories were told in broken English, and with a spellbinding conviction. They had added force because his stepfather seemed to be telling no one else, mainly because no one else, including his new wife, seemed to want to listen.

In many ways, it was an idyllic father-son relationship. "I used to find him fascinating, the things he told me about his home town, the forests and the swamps, the rivers. We used to go to the woods to pick wild mushrooms."

John immediately felt even closer to his new father than to his mother. The relationship grew more intense as the years passed.

His new father had had a first wife in Britain, a shadowy figure whose baby had died and who was now living in a mental home. That tragedy apart, Chrzanowski was prospering in post-War Britain. He spoke little English, but there was a Polish expatriate community in Birmingham and a Polish doctor should anything arise that was too complicated for him to explain in English. Not that poor health was a problem. One of the reasons John admired his new father was that he had apparently limitless physical strength. Stan, as he was known, worked as a skilled machine tool operator in the car industry, where overtime was plentiful, trade unions were strong, and he was bringing home good money.

His wife was wilful and short-tempered like him, but they complemented each other. Where he came from, men did no domestic chores, but although he could not cook, he taught his wife to cook in the way he liked, with garlic, and to make tea without milk. She filled in his forms, sorted out the bureaucracy, and by the end of the Fifties her new husband had become a British citizen and had adopted two English children.

In this new, secure family, John's admiration for his stepfather rose. Chrzanowski had told him that he had once been a commando. Trying to emulate his deeds, John jumped from a high wall - and ended up in hospital as a result. The sepia pictures his father had brought with him showed a handsome young man in uniform. To a Birmingham schoolboy, a uniform was just a uniform. John never asked what it represented.

His father told heroic stories of how, during the War, he had disabled Russian tanks with makeshift petrol bombs. He made toy guns and knives as presents for his son. His father's War, John realised, had been different from that of other fathers in Birmingham. His father, he learned, had come from Slonim, a town in a part of Poland which was now in the Soviet Union: he had fought for both the Russians and the Germans.

As John and his friends swapped stories about their fathers in the playground, playing the perennial game of one-upmanship, John thought the stories he could retell were better than anything his friends' fathers had done in their flying bombers, or their desert fighting. Yet, puzzlingly, when he told his father what he had done, he was scolded and told never to repeat the stories again.

Other incidents were more disturbing for a child. "We used to have chicken on a Sunday. When you pull the leg off, you can pull the tendons and make the claws sort of go out. A little thing like that would spark him off - he would talk about bodies being burned, the tendons being pulled into strange shapes, about piles of bodies by barbed wire, and having to climb over them." No wonder his mother told her husband to shut up and leave the table. But the boy took in what he heard as dramatic stories, not as reality. Horrified but fascinated, he would go off alone with his father, to hear more, entranced by the way his father would mime the actions to go with the tales.

"My father used to tell me about killing people, and how it was done, in quite graphic detail. When he described killing children, he would say how you lead a little toddler to the edge of a building and then would mime grabbing the child's ankles, and whipping it against the walls, and he'd do it in a very smooth motion, almost bear-like."

These executions, his father always said, were things he had seen, not things he had done. But the love which was deepening in John for his father was tinged, perhaps made more intense, by fear. It was a less humane time than today, and thrashings and canings of schoolboys were not uncommon. But those at the Chrzanowski household were particularly severe. "He worked at Dunlops, and brought these pieces of rubber home, solid rubber used in sports equipment. And he got my mother to use this on me, which she did until she saw the welts. It would sort of hit round you and whip on the other side of you."

There is a picture of John's father with a German Shepherd dog. According to John, he used to beat the dog in the same way.

Looking back now, John Kingston is puzzled that he never pieced together the various recollections and his stepfather's cruelty, but left them as a series of tales, episodes, something he accepted. "I'd kept everything he told me as a child as separate incidents," he says. "For some reason I'd never put the pieces together." He wonders now if that was a psychological defence mechanism. "Maybe you keep things in your mind distinct from each other, so that you don't realise the full significance."

Besides, his father spoke in broken English, in a stream of consciousness, one tale leaping into another. And he had a savage temper. He was not a man you could interrupt, or ask to clarify a point. That was how his father was; these were the things he had done. Consciously, John was only aware that there was a tension in the household which he found increasingly hard to stand.

He left school and trained first as an electrician, then as a psychiatric nurse. The easiest way to cope, he had found, was not to confront the problems in his family, but to put them behind him. In 1965, aged 21, he married, gave up his job as a psychiatric nurse, changed his name back from Chrzanowski to Kingston, and moved to the Yorkshire moors, 150 miles away. He had, superficially at least, escaped, and now had minimal contact with his stepfather. Occasionally he would remember the odd incident from his stepfather's War stories, mention it to his wife, Sheila, then put it out of his mind.

There was little time for contemplation. Life was busy, living on a remote farm, working in a textile mill to make ends meet and bringing up their three children. And there were tragedies to contend with. One baby died of spina bifida at the age of 18 months. Two more were stillborn. But, despite all that, John knew he had not really escaped his father's influence. "I made myself physically fit, because he believed in physical fitness," he says. He even became a professional wrestler - the sort of activity his father admired.

It was not until 1987 that events conspired to make him, at last, begin the painful task of trying to pull the separate strands together to identify his stepfather's real past. He took a pause from his career, which had by now moved from textiles to retail management, and took a degree in business studies as a mature student at what was then Huddersfield Polytechnic.

His eldest son died of meningitis, aged 17, which prompted him to think about death, and, with his greater leisure time, to dwell on the experience and emotions of losing family. Meanwhile, he and his wife had been watching on television the trial of Jan Demjanjuk, an alleged brutal killer at the Treblinka death camp. Then he saw an advertisement in a newspaper from a Home Office War Crimes inquiry, seeking information and names of suspects living in Britain. In both cases, the suspects were not German, but people who had collaborated with the Nazis in German-occupied territory. John Kingston thought hard about his father's stories. Could he possibly have been involved? John wrote the stories down, and sent them off to the inquiry.

As soon as that letter was in the post, John realised that all he had sent off were fragments, and that he had no idea about his father's life. All he knew about his father's arrival in England was a simple childhood story that he had escaped from Poland and joined the free Poles.

By this time, John Kingston had completed his degree, which had given him the training and thirst for research. So he decided to pursue his family history. Where for other people this is a hobby, for him it became an all-consuming passion: he decided to take a year off to allow him to work on it full-time. That year has now stretched to seven, while Sheila works to support the household.

John worked his way backwards, starting from the time when his stepfather arrived in his life in 1953. He knew Stan had first settled in Oldham, only 15 miles across the Pennines from Holmfirth. He began to go there and talk to people, and found the marriage certificate of his father's first wife, a Czech woman who had died in 1984. In the dusty archives of the local newapaper he found the records of the daily lives of the immigrant communities, and one sad copy of the Oldham Evening Chronicle for 24 January, 1951, recording how "on a charge of infanticide, a foreign worker, Toni Chrzanowska, 23, married, who had been lodging in Keresly Street, was committed for trial at Manchester Assizes".

She had been found in November with her half-strangled six-day-old boy in the maternity hospital, and the baby had died four days later. "The accused had seemed quite cheerful and unaware of anything untoward having happened," the report said. John looked up the birth and death certificate of the baby and visited the graveyard where it was buried.

He discovered that his father had been one of tens of thousands of European Volunteer Workers allowed into Britain in the late Forties to plug a huge manpower shortage in the mines, the mills and the factories left by the War. Poles were seen by the British authorities as good workers, good stock to assimilate into the British nation. John Kingston found the remains of a volunteer workers' hostel in Ashton-under- Lyme where his father had lodged when he first came to Lancashire.

All the time, he was coming to the inevitable conclusion that research could only get him so far. Answers were needed which only his father could supply. In 1990, he telephoned his father, who by now had retired to a village near Telford, in Shropshire, and went down to stay. The War Crimes Inquiry, his father said, had been to see him, but he had shown them his medals from fighting with the Allies in Italy, and they had gone away. They had not, apparently, been looking for anyone from Slonim.

"So we started talking about it," John says. "I didn't need to ask him, I just needed to listen to him and coax him a little." He went again and again, and spoke on the telephone, recording every detail in a notebook or on tape.

There was a difference from their earlier childhood conversations, because John had now armed himself with the tortured history of Slonim during the War years. At the start of the German occupation, it had been home to 22,000 Jews. By the end, all had been killed or driven out as part of Hitler's Final Solution. When the War began, Germany and the Soviet Union had shared out the map of eastern Europe between themselves, putting Belorussia and eastern Poland, including Slonim, under the Communists. In 1941, the Germans had taken it as they swept into Russia, only to see it go back to the Soviets again in 1944 as Germany was defeated.

The problem for John Kingston was that if he was better placed now to understand and cross-examine his father than he had been 40 years earlier, so his father - who was born in 1921, and was a young man during the War years - seemed to him to have become less straightforward.

In one account, he said he had escaped to Liverpool in 1939, and been parachuted back into Slonim as a British agent in SS uniform. Sometimes, he said he had worked in a factory up to 1943, then joined the Belorussian army. At other times, he admitted he had been an auxiliary police guard at the German police barracks.

At this stage, John says that he was still only interested in family history, in finding out the truth for his own purposes, not to try to have his father prosecuted for anything he might have done. When his father produced wartime photographs John could not remember seeing as a child, he checked them against reference books. One, he decided, showed his father in the uniform of the German auxiliary police, local battalions of which were set up all over eastern Europe to serve under the SS.

The conversations were frustrating. His father told him that some of the stories from childhood, such as the ones about burning Soviet tanks, had been things others had done. "I only told you because I wanted to be a hero to you," Stan told his stepson. But John was unpersuaded. There had been too much detail, he had witnessed too many incidents. He was convinced no one could know so much without being involved. It was like clutching at something which constantly slipped from his hands.

By 1993, John had despaired of finding the whole truth. He decided to try to reconcile himself to whatever it was the older man had done in a different way. Perhaps, John reasoned, his stepfather had done terrible things, but with the best of motives - "Perhaps he was on some sort of religious crusade. Perhaps he now feels some remorse."

John decided to put this to an extraordinary test. For three weeks he travelled with his father around Russia, ostensibly to visit his father's sister and her family, now living in Volgagrad. His stepfather showed no regrets for what had happened to Jews and Communists under the Germans. The experience effectively turned John Kingston from family historian to prosecutor.

Early last year, he passed copies of the family photographs, auxillary SS-style uniforms and all, to Scotland Yard, together with a list of his father's Polish friends who might be persuaded to tell the police what they knew, or might already be on a wanted list.

The same dossier was given to the Belorussian consul in London, and to the Soviet Embassy, in the hope that they would check their records. The Belorussians passed Kingston's name to a Sunday Express journalist who was about to fly to Minsk to investigate a different war crimes suspect. Slonim is close to Minsk, and Kingston gave further copies of photographs to the journalist to check whether anyone in his father's old home town remembered him.

Many said they did. His name, they volunteered on seeing the pictures, had been Chrenowski, a slight variation. One old woman, Alexandra Dalevsky, said, through an interpreter, that on 28 June, 1942, Chrenowski and another guard had taken her husband and 120 other civilians to an execution pit at Petralaevichi, a farming hamlet near the town. Her husband was shot dead. She said of Chrenowski: "He was very proud of wearing uniform and carrying a weapon at such a young age. He was extremely cruel."

Another ageing resident, Kazim Adamovich, looked at the photographs and said: "I knew him and his elder sister Vera very well during the Nazi occupation." He said Chrenowski had volunteered to join the police after the Germans invaded in June 1941. "He would visit the makeshift prison. His job was interrogating prisoners who were later taken away to be shot."

Armed with these witness statements, John Kingston felt vindicated in his belief that his stepfather had been involved in something serious. Nervously, he telephoned his father and held two conversations, lasting almost three hours in all, in the pidgin English they have always used to communicate.

Laughing, his father told his son off because the police had been to see him. Then his son, apprehensive but persistent, put the accusations to him. Witnesses in Slonim, he said, describe you leading civilians away to be killed.

"These two women, they living by where you live near sawmill, say your uncle has shop and sawmill not far from your house. These two women, they know you and they see you go every day pushing people to take them to be shot by the Germans .... Why these people say these bad things about you?"

"I don't know, John," his father said. "But it is not about me, maybe it is somebody thinking different one man."

He had never been more than a guard, he said, how could it have been him? All right, he conceded, he did see naked people being herded through the streets, but he only watched. All the killing was done by Latvians. No, he was never in the SS, or anything to do with the SS.

It was the last conversation between them. Since the Sunday Express ran an article about his father, the two men have not spoken. All journalists trying to contact the old man since then have been told he does not want to talk. John Kingston's mother no longer has any contact with her son.

John Kingston feels he has reached another plateau in his search for the truth about the past. Detectives from Scotland Yard came to see him this year to say they were going to Slonim to interview witnesses, but since they returned they have not spoken to him. The Belorussians say they have agreed to say nothing to him unless Scotland Yard agrees.

Now he believes he can only reach the end of his odyssey if he journeys to Slonim himself, to hear and question first-hand the survivors. There is another part of him which would like to let the whole matter rest. Why not leave an old man, who is not even his real father, in peace, or let the responsibility for finding out the truth rest with the authorities? Why he cannot do so is almost as much a mystery to him as it is to the outside world. It seems as though the quest for his stepfather's past is, in some sense, a quest to discover something that explains his own history, too.

"I saw my natural father just before he died," he says. "I was surprised I'm nothing like him. Even though Stan and I were apart for so many years, I'm surprised how much like him I am - even my build and face. People see me as his son - I don't know if it's because he's brainwashed me and I've modelled myself on him. Being a parent and being a child isn't just a biological thing."