Is loneliness making the Home Secretary risk his political life?

David Blunkett's friends are dismayed and baffled by his readiness to risk his political career in pursuit of his love affair with Kimberly Quinn. Those who have known the Home Secretary for years say he is headstrong but also deeply ambitious and has ruined any hope of becoming Prime Minister with his determination to prove he is the father of her children.

David Blunkett's friends are dismayed and baffled by his readiness to risk his political career in pursuit of his love affair with Kimberly Quinn. Those who have known the Home Secretary for years say he is headstrong but also deeply ambitious and has ruined any hope of becoming Prime Minister with his determination to prove he is the father of her children.

"He is a deeply religious man, and he clearly thinks he is right," one close friend said. "Even though he broke up from his wife, he is committed to his three sons. And if he thinks he has children by Mrs Quinn, he will think it is right he should look after them as the father."

Mr Blunkett, 57, has overcome the disability of blindness from childhood to climb the political "greasy pole'' to the Cabinet. To do so, required enormous self-belief and a determination that few colleagues can match. But those who know him say he is very lonely figure. "He is totally committed to politics," a friend said. "He has not much else in his life and he is very lonely. I think that is part of this."

Mr Blunkett admits to loneliness in his autobiography, On a Clear Day. He also describes the pain of being taken away from his parents to go to a special school at the age of four. "I desperately missed the hugging and affection of home ... this deprivation had a lasting effect on me well into adult life."

The Home Secretary, who has three sons from his marriage, added: "Although my own sons are now growing up fast, I often give them a hug chiefly because I believe it is important for them to feel that somebody cares about them."

Behind the "cuddly" side to Mr Blunkett is a calculating and shrewd politician, who has cultivated a high public profile, which from has suited Tony Blair. When the Blairites wanted to a show of strength to combat Gordon Brown's ambitions for No 10, they turned out in force - Cherie Blair, Alastair Campbell, Alan Milburn, Stephen Byers and Peter Mandelson - for the publication of a pamphlet on New Labour themes by the Home Secretary.

His image as a hardline home secretary has also enabled Labour to outflank the Tories on its most vulnerable ground. He has supporters in the right-wing popular press who applaud his stance on asylum-seekers and crime.

He was never a liberal intellectual and he needed to be tough to become leader of Sheffield City Council in the 1970s, known as the "Socialist Peoples' Republic of South Yorkshire". But he is seen as a pragmatic politician.

Mr Blunkett was born blind, a victim of a one-in-a-million genetic accident: doctors told his parents their genes were not compatible and the optic nerve behind each eye failed to develop. His mother, Doris, was 43, and his father, Arthur, was in his mid-50s. Arthur, a widower, had four children from his earlier marriage. Doris, who was divorced, had one daughter.

The shock of his blindness, which turned his mother's hair temporarily white, was compounded when Arthur died in agony after being scalded at work in an horrific industrial accident. From that moment, David Blunkett learnt about prejudice and hardship.

As a naive 16-year-old schoolboy he was taught to kiss by a childhood sweetheart, Pamela Edwards, who worked in a factory. "Pamela made me feel special, that I deserved to respect myself and that I could lead a normal life."

Life continued to be a fight: he had to fight for the right to take O-levels, and attended night school to enable him to study politics at Sheffield University. He met his former wife Ruth Mitchell at college and they married as soon as they graduated.

They have three sons, Alastair, 27, Hugh, 24, and Andrew, 22. When they divorced in 1988, after 18 years of marriage, he said: "As we grew into middle age together, we began to realise that we were not compatible."

Mr Blunkett has kept close to his sons, and revealed that one of his boys, who works in the computer industry, was a strong campaigner against the introduction of ID cards and regularly gave him "a terrible hammering" on the question. They had "some very good family disagreements", although another son was a strong supporter.

In the summer, when news broke of his affair with Mrs Quinn, Mr Blunkett was on holiday with his three sons, and an old friend from Sheffield, Paul Potts, editor-in-chief of the Press Association. Mr Blunkett said: "After my divorce I decided not to talk again about my subsequent private life.

"I have stuck to that principle over the years, whatever the pressure to confirm or deny a particular story and defended all politicians' right to a degree of privacy in their private life."

At boarding school, there was nowhere he could be alone, he said in his book. "Privacy is something I came to value greatly," he added.

Last night, that privacy had been shattered by his claims to be the father of Mrs Quinn's son, and the baby she is expecting in the new year.