Lifting the veil on the influence of religion in his life, Mr Blair says that he has to live with the decision he made over Iraq and with his conscience. In the end there would be a judgment but “if you have faith about these things then you realise that judgment is made by other people”.

Asked by Michael Parkinson in an interview to be screened tonight what he meant by that, Mr Blair replies: “By other people. If you believe in God, it is made by God as well . . .” Faced with decisions about people’s lives and in some cases their death, “the only way you can take a decision like that is to try to do the right thing, according to your conscience and for the rest of it you leave it to the judgment that history will make”.

Mr Blair’s remarks, on ITV 1, may cause discomfort among some in his party and in the country who were opposed to war. Politicians have traditionally been highly cautious about suggesting any religious influence on their decisions.

Mr Blair breaks new ground in other areas in the course of the interview. He speaks of his friendship with Gordon Brown, at the same time admits that their relationship has sometimes been difficult, and voices understanding for the Chancellor’s desire to take his job.

He tells of the time his father-in-law, Tony Booth, visited the newly-wed Blairs’ house and asked if it would be OK to smoke cannabis. Mr Blair apparently gave the go-ahead. He speaks of his admiration for Bill Clinton, “the best politician as a politician I have ever come across”, and his “easy and straightforward” relationship with George Bush.

Mr Blair also reveals that it was religion that sparked his interest in politics. “There were people at university who got me into politics,” he says. “I kind of got into religious politics at the same time in a way and until the age of about 20 I really wasn’t interest in politics at all.”

Mr Blair speaks about his heart operation and discloses that recently he rang up a woman who was about to have a similar procedure to reassure her. Her mother had sent him a letter saying she was about to have the same operation, was terrified and Mr Blair was the only person whom she knew had had it. He says that when he went to the hospital the surgeon started explaining the operation to him and he replied: “Look, I do my job. You do your job. I don’t want to know anything about it.”

He says that when the doctor who was sedating him came over his hand was shaking and he had said: “You’re the Prime Minister, what if something goes wrong?” Mr Blair replied: “What do you mean, if something goes wrong? Just stick it in.”

He again speaks of his closeness to his father. He says that his father joined the Army as a private and came out an officer: “He went in as a young Communist and came out a Conservative.”

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