As the star of television drama The Affair, Ruth Wilson played a fictional cheating wife - and now she is set to expose real-life adultery in her own family.
In a new BBC
series Surrey-born Ms Wilson, 35, will play her grandmother Alice, who found out on her husband Alec's death that he was a bigamist.
It later transpired that Alec, an MI6 agent and author, had four wives and four families over the course of 30 years.
In t he three-part Mrs Wilson, Alice learns the truth when a woman turns up on her doorstep claiming to be the 'real' Mrs Wilson.
Alice sets out to prove that her own marriage was genuine – only to unearth more disturbing secrets about Alec.
In real life, Alison, who was married to Alec for 22 years and bore him two sons, Gordon and Nigel, only learned part of the shocking truth after he had a fatal heart attack in 1963.
He had given Alison a number to call if he died. So she rang it. Hours later, a Gladys Wilson turned up at her home in Ealing, West London. She claimed to be Alec's wife and the mother of his kids Adrian, Dennis and Daphne.
Ms Wilson, who also starred in Luther, learned of the scandal at 18, when her grandmother let her read a memoir she had written.
After Alice's death a journalist discovered that Alec had two further wives and a son with each.
He had also been arrested for fraud, theft and falsely wearing a colonel's uniform and medals. And he had written 18 spy novels as Alexander Wilson, drawing on his MI6 experiences.
Ms Wilson told The Sun:
'It was quite an interesting process because my grandmother wrote her memoir with a perspective... she only knew about one wife.
'She had destroyed anything else that had any mention of my grandfather — any diaries or anything else. So she had this one thing that she was giving to the family, that was her narrative, her journey.'
'When she died, a year later, we had two correspondence from two people to my uncle saying they thought they had the same father. My granny in reality only knew about one wife and, thank God, she didn't really know about those two.'
Alison wrote in her memoirs that the only thing she really believed of the man she was married to for 22 years was that he was full of lies.
She wrote: 'He had not only died, he had evaporated into nothing. He had destroyed himself. There was nothing left but a heap of ashes. My love was reduced to a heap of ashes.'
A few genuine facts are known about Alexander Wilson, known as Alec. He was born in Kent in 1893 to an Irish mother and an English sergeant in the British Army hospital corps and grew up moving from base to base, including Hong Kong, Singapore, Mauritius and Ceylon.
He wanted to follow his father into service and trained as a pilot, but a knee injury prevented him from fighting in the First World War. In 1916 he married his first wife, Gladys. Their first child, Adrian, was born a year later.
After the war Wilson became a purser in the merchant navy but was prosecuted for theft. After six months' hard labour, he and Gladys started a touring theatre company and had two more children, Dennis and Daphne. He also wrote two books based on his experiences in a touring troupe.
Everything changed in 1925 when, out of the blue, he was appointed professor of English Literature at the University of Punjab, a troublesome region of the British Raj in India.
Tim Crook, an academic and journalist who spent six years investigating Alec's life and wrote a book about him called The Secret Lives Of A Secret Agent: The Mysterious Life And Times Of Alexander Wilson, is convinced that this was the start of his work for the intelligence services after discovering letters from Alec begging to be allowed to serve either as a soldier or an agent.
'The academic who appointed him at the university had connections with the intelligence world,' Tim says. 'I suspect some Army connection, possibly through his family, led to him being either recruited or activated at this point. The British needed to combat the threat of Communist-backed insurgents on the Northwest frontier.'
Alec became an honorary major in the Indian Army Reserve, and with his academic cover allowing him to spy, he travelled across Ceylon, Arabia and Palestine while Gladys and his children remained in England. He also began writing a series of spy novels that became a critical success.
While professionally he was already leading several lives – as a spy, a novelist and an academic – things became even more complicated when Alec met and married a touring actress called Dorothy Wick and they had a son, Michael.
They returned to Britain in 1933, but while Dorothy and Michael lived in London for a year and a half, Alec went back to his first family and his only legal wife, Gladys, in Southampton.
Dennis Wilson, Alec and Gladys's son, later recalled: 'My father had been this rather glamorous figure who would turn up on leave driving a flash hired car and bringing us loads of presents before leaving again.
'The 18 months he lived with us after he returned from India were the only time we were a family.'
That happy existence – all of Alec's children seemed to adore their father – ended in 1935 when he left Southampton for London, saying he was going to look for somewhere for them to live in the capital.
But he never sent for his family; instead he moved in with his second wife Dorothy. 'I imagined him arriving at Waterloo with his luggage and looking for lodgings,' said Dennis. 'But I now know that all he did was return to Dorothy.'
In 1940 Alec joined MI6, eavesdropping on conversations held by foreign embassies.
He also began a relationship with Alison McKelvie, an MI6 secretary and Ruth's grandmother. A year later he left Dorothy and his second family to start his third.
Michael remembers being seven the last time he saw his father in 1941 on a railway platform; by then the family had moved to Yorkshire. Alec was in uniform and going off to war. 'Don't cry,' his father told him. 'There's a brave chap. I won't be away long, you know.' A few months later, a maternal uncle told Michael that his father had died an honourable death at the battle of El Alamein; all Michael was left with was a photograph album and one of his father's novels.
But Alec had not gone to war. He'd only travelled as far as London to live with Alison, who he had married, and they had a son Gordon.
Alison had known he was married (to Dorothy) when they began their romance, but believed he was now divorced. Still barely out of her teens, she recalled a charming older man who was known as 'Buddha' at MI6 because of his experience in India and fluency in eight languages.
He also told her he was related to the noble Marlborough family and Winston Churchill. His ancestral home had been requisitioned for war work, he added. As she was soon to find out, none of this was true.
Not even the name he had given her; he'd changed his middle names for their wedding certificate so nobody would realise he'd been married twice before.
In 1942, shortly after the birth of Gordon, he was dismissed from the Secret Service.
He told Alison this was for 'operational reasons' and he was now an agent in the field, but all she knew was that suddenly the family were plunged into poverty and insecurity.
In 1944, while Alison was pregnant with their second son Nigel (Ruth's father), Alec was arrested after attending Mass for wearing a fake colonel's uniform and medals. He told Alison this was a contrivance enabling him to infiltrate subversive groups in prison.
Four years later he was arrested again, this time for embezzlement at the Hampstead cinema he was managing. He wrote four unpublished spy novels after the war but spent most of the years between 1948 and his death in 1963 working as a hospital porter, then as a clerk in a wallpaper factory.
The family had little money and moved house 17 times in 17 years, often just one step ahead of their creditors. All the while, Alec insisted to an increasingly sceptical Alison that it was all part of MI6's plans.
Astonishingly, in 1955, he married yet again after meeting a 26-year-old nurse called Elizabeth. She became pregnant with another boy, Douglas, and for two years Alec carried on a double life with Alison and Elizabeth until Elizabeth moved to Scotland.
Ruth wonders now if he married bigamously so many times through a sort of misplaced sense of duty. 'He never just got a girl pregnant and ran off,' she says. 'He felt he had to keep marrying them.'
To avoid upsetting her two sons and causing a fuss, Alison asked Gladys to pose as a distant relative at the funeral. 'My Uncle Gordon was a captain in the Navy,' adds Ruth. 'And when he appeared in uniform Gladys almost fainted because he was the image of the military man she had married nearly 50 years before.'
It was only when Tim Crook, who was investigating Alec on behalf of Michael, the son of wife number two Dorothy, got in touch with his findings in 2006 that Ruth realised what a story it was.
'It got too big for us to ignore any more,' she says. The shock was immense, although fortunately none of the wives were around to understand the extent of their husband's duplicity; three were dead and one was suffering from Alzheimer's.
In 2007, a gathering was organised where nearly 30 of Alexander Wilson's relations met for the first time.
Despite the difficulty of the circumstances, they were all pleased to have found each other, particularly the seven half-siblings who discovered they had much in common.
Alec had raised all his children as Catholics and taught them to be patriotic, 'modest, humble, strong-willed and caring', says Ruth Wilson. All of them enjoyed sport and many of them had joined the forces.
The BBC1 drama will air on November 27.