EVEN while headlines discussed details of affairs and DNA paternity tests, David Blunkett was determined to keep his private and political life separate.

Close friends say the home secretary is a ''lonely guy'' who strictly compartmentalises every aspect of his life.

Ever since the News of the World broke the story in August of Mr Blunkett's relationship with Kimberly Quinn, the publisher of the Spectator magazine, the home secretary had refused to comment on the details of their three-year affair.

This was despite reports that he was not only the father of her 26-month-old son, William, but could also be the father of Ms Quinn's unborn child.

Friends say he is ''horrified and mortified'' that he has now been forced to call for an independent inquiry.

Mr Blunkett's friends and colleagues believe he will survive the scandal if no other damaging titbits emerge, but they admit that ''the whole sorry episode'' has left grave questions over his judgment.

One asked what a man of his age was doing having unprotected sex with a married woman only weeks after her wedding. Another, more sympathetic, understood why he wanted to play a role in the upbringing of his child but admitted that he should perhaps be thinking more about what was in their best interests.

He said: ''David Blunkett is a really lonely guy. He wants access to his kid or kids. He deeply, passionately adored their mother and in spite of the humiliation and embarrassment in which he is now embroiled he wants to do what he considers to be the right thing by his children.

''David is not a financially generous guy so this is not about throwing money around. This is about him wanting to take care of his kids, but I know that others would say that the best thing for the children would be to leave it alone.''

Yesterday, an e-mail in a newspaper appeared to reveal Mr Blunkett was the father. The couple were said to have had a private DNA test last year. However, the couple's relationship has deteriorated and Mr Blunkett is said to have threatened to use the law to gain official recognition of his fatherhood of William.

A friend of Mr Blunkett said: ''There was a paternity test and he and Kimberly took elaborate measures to ensure that they opened the envelope together. The test was quite clear. All that stuff about evidence that (Stephen) Quinn is the father is the precise opposite of the truth.''

Although Mr Quinn, the man she married nine weeks before she embarked on an affair with the home secretary, believed he was the baby's father, and did so until a few days ago, Mr Blunkett had insisted on proof of paternity in 2003. He is also expected to try to establish the paternity of the baby with whom Ms Quinn is currently seven months' pregnant.

Until three months ago, Mr Blunkett had cherished the hope that Ms Quinn would heed his pleas and leave her husband to set up a family home with him, but now friends say he has accepted he will never realise his dream and that he knows the situation is hopeless.

A friend who insisted Mr Blunkett ''would never, ever wish'' for the details of his private life to be made public, said: ''You have to understand that David was involved in an intense and loving relationship with a woman he was convinced he could look after and make happy. He asked her many times to leave her husband and he promised to take full responsibility for William.''

Now his friends say he only wants her to acknowledge his role in William's life, to let him be involved in his life, and support him as any decent father should.

Another aspect of the home secretary's silence to allow close associates to speak up on his behalf is the hope that if he can prove that this is a woman who is prepared to lie to her husband about the paternity of her son, anything else she says will be taken with a pinch of salt.

Amid a string of accusations, she has claimed he fast-tracked a visa for her Filipina nanny to let her stay in Britain indefinitely. Mr Blunkett has vehemently denied this and assured the prime minister only yesterday morning that the claim was not true. Civil servants also deny press reports that two of their colleagues asked Ms Quinn to sign a statement saying her marriage was in name only and was over.

Mr Blunkett is down but not out. Tony Blair and friends and colleagues, though shocked and astonished at the complications of the embattled home secretary's love life, are standing by him, insisting his private life should have no bearing on his public role.

Mr Blunkett can expect a rough ride in today's papers. In Downing Street they will be more interested in watching how he survives today's Commons performance during the Queen's speech debate on security issues. There is little doubt the prime minister will show him the door if he suspects the turmoil in his personal life is having an impact on his work.