The ambitious leader of Unison - Britain's biggest union - knew where he was going. But not where he came from. A family story cast him as the love-child of a pretty young nurse from Yorkshire who had a brief romance with an Irish carpenter in wartime London.
Fifty years later, the tale came true in a quiet Dublin restaurant where he was reunited with three Irish brothers he never knew existed.
Rodney, 53, fought to hold back the tears as he declared: "It's wonderful. Suddenly I've got a whole new family and they're such lovely, friendly people."
The story goes back to the 1830s when the Bickerstaffes began migrating from the village that bears their name near Ormskirk, Lancashire. Some of them settled in the mining country of South Yorkshire, where the living was hard. His great-grandmother Elizabeth died in the Doncaster workhouse as late as 1925.
Rodney's mother, also called Elizabeth, was born in 1920, the eldest of 10 children. At one time, the family was so poor they lived in a railway carriage in a gypsy field. But Elizabeth worked her way through high school and was training as a nurse when the Second World War broke out. She finished her training in Whipps Cross hospital, east London, when Nazi bombers were wreaking havoc. One day in 1944, a young Irishman walked into casualty complaining of stomach pains.
The man was Tommy Simpson, who was working in the capital with his father. He was handsome and charming, and soon he and Elizabeth were courting. In the way of wartime romances, Elizabeth found herself pregnant in the summer of 1944. But Tommy went back to Dublin and never got in touch again.
The abandoned young nurse gave birth to Rodney Kevan Bickerstaffe in Queen Charlotte's hospital, Hammersmith, west London, on 6 April 1945. She wrote to Tommy's sister to let the family know she had his son but there the contact ended.
In those days, there was still a stigma attached to single motherhood. Rodney even had a special birth certificate, which did not name the father.
Elizabeth raised her baby in an unmarried mother's home and then moved to the University Settlement in Bethnal, east London, where she worked as nurse to a professor. When Rodney was two she moved back to Doncaster to live with her forgiving parents. Mother and son shared a bedroom in the rented Victorian semi occupied by sometimes as many as 10 of the Bickerstaffe family.
Elizabeth was determined to build a new life for herself. She took a job as a nurse in the local day nursery, eventually rising to be matron.
Gawky, bespectacled Rodney learnt the rudiments of the three Rs there. In the school playground he fought with boys who taunted him about not having a father. "I think I gave one of them a bit of a thrashing, even though he was bigger than me," he admitted.
When he was 11, Elizabeth asked him if he would mind her marrying Norman Topham, a local man whose marriage had ended in divorce. Rodney knew Norman's son, Peter, who was three months younger than him and was at the same school. Elizabeth and Norman married, and she destroyed virtually everything she had saved from the fling with Tommy, except for one small picture.
"She started life all over again," Rodney recollected. "My new dad was as good as gold. He was a wonderful guy."
All thought of his natural father went out of the window. But he kept the name Bickerstaffe and won a place at Doncaster Grammar School.
The rest of Rodney's career is history: His rise in the public employees' union Nupe and his coup in bringing together three unions to form a single public-service union. And his determination to achieve a national minimum wage - which will happen next April.
His passion for trade unionism was inherited from his mother, who joined Nupe as a trainee nurse in 1940 and is still a union member 58 years later.
The extraordinary story might have ended years ago, with no one any the wiser about his "other family" in Ireland. But when Norman Topham died in 1990, Rodney began to ask his mother for more details of his origins. It was an emotional ordeal for his mum. But she told him the facts of her wartime romance.
Rodney did not strenuously try to find his natural father, until in the spring of this year - after discussing it with his wife and when his mother, now 78, had fought off cancer - he finally decided to look for him.
His mother divulged a last-known address in Cabra, on the outskirts of Dublin. In late September, he was in the Irish capital for a union conference "I took a taxi to the street and knocked on the door," he told me. "There was no one in but a next-door neighbour said the home was still owned by the Simpson family."
The elderly neighbour mentioned that another member of the family lived a couple of miles away. Rodney decided that this man, 88, was too elderly for such a shock. He simply told him that they might be related, and the old man offered to get his daughter Ann to speak to him later. Rodney had to catch an aircraft but telephoned Ann as soon as he got to Dublin airport.
"This is a strange story," he told her. "There's no simple way to say it, other than we are cousins. You had an uncle Tommy. He was my father."
Rodney recalled: "I explained enough for her to believe me. I said I was a trade union leader in England, and I was about to board a plane. She wanted to see what I looked like and I said I would be appearing on Question Time the following Thursday. I asked if her uncle Tommy was still alive and she said no, he had died in 1991."
Then came the big shock. On his return to Dublin from England in the Forties, Tommy Simpson had married a local girl, Eileen, now also dead. Scarcely able to contain himself, Rodney asked: "Did they have any children?" "Yes," Ann said. "You have got three brothers." Tom Simpson, 49, Liam, 47, and Frances, 45. They were all married. Four of Tommy's sisters also survived.
They agreed to leave things until after the Labour Party conference, starting in Blackpool that weekend. Events moved quickly, however. His aunt Maureen, who had been unaware of the secret, spoke to him on the phone and broke the news to his brothers.
Tom's wife, Breda, was vacuuming the house the next morning when Rodney appeared live on Breakfast with Frost. "It's him!' she shouted to her husband. Tom leaped out of bed and exclaimed: "He's the image of my father."
Once they began talking, remarkable similarities between the families emerged. They were both steeped in trade unionism - Tom's mother had been a pioneer of the Irish Women Workers' Union. Rodney and his brothers had both been partly brought up in their grandparents' home - Tommy Simpson's marriage broke down after a few years and he returned to England.
Son Tom had watched Rodney speaking at the Labour Party conference without realising he was his brother. "I used to see this Buddy Holly figure and think `He's a man after my own heart'," he said.
Once they got over the shock, the three brothers welcomed Rodney with open arms. Rodney himself had had doubts before setting off on his voyage of self-discovery. He said: "I wanted to shut down the story because it never struck me that after 54 years there would still be anybody living at the address my mother gave me. I hoped to find something but I didn't expect to."
He talked to Clare Short - who had recently rediscovered her long-lost son, Toby - about how to handle the experience and discussed it with his mother. He said: "She was sorry that Tommy had died but it had been such a long, long time... she's a very proud person, a strong person, a very independent person - a real tyke.
"My reaction was first, I've got this new extended family, and second, that the Irish connection is fascinating. I have had a very full and happy life... But at my time of life it's a wonderful bonus."
It has meant a few jokes at his expense. Pauline Prescott, the wife of the Deputy Prime Minister, smiled: "I always knew he had kissed the Blarney stone." And Tony Blair, who privately met up with Rodney and Tom at Westminster, joked: "Fancy waking up in the morning and finding that you have got Rodney for a brother."
The Unison leader said: "Tony thought it was a great story and said how pleased he was." Tom said: "The mums were the heroines, bringing us up on their own. They had a real struggle. It was blood, sweat and tears."
But the tears were not for nothing, as the happy faces round that Dublin restaurant showed.
This article was first published in yesterday's edition of "The Mirror"Reuse content