When Metropolitan Police Commissioner Sir Peter Imbert had a heart attack two years ago, he realised there was a distinct possibility he might die. Journalists were waiting outside his hospital door firming up his obituary details, which he was determined not to give anyone the opportunity to publish. ‘I’ll make a bargain with you,’ he said, post-intensive care, ‘you show me my obituary, and I’ll talk to you.’ No interviews ensued. Sir Peter, 59, retires on Sunday after a distinguished and extremely hard-working career. He imagines his obituaries might have said that he’d endeavoured to change the face of policing. But now he’s talking in a rare way about everything from his neglect of his family, to his passion for his wife and his son stealing money.

He’s sitting in his massive New Scotland Yard office in suit, white shirt and vest. His manner is charming but he appears tired and has hamster cheeks. He wears his identity card, having recently been refused admission to a police conference by a Lancashire constable.

Sir Peter is known for negotiating with the IRA terrorists cornered for a week in the Balcombe Street siege in 1975. He was also involved with the Guildford Four, who were subsequently freed in 1989. (He took a confession from Hill, in connection with the Woolwich bombing, and interviewed Conlon after his Guildford conviction.) Shortly after their release, he was quoted as saying: ‘You’re probably hoping that I’m going to say that the freeing of the Guildford Four was one of my worst moments, because I was involved. But it wasn’t. I just hope it won’t taint such reputation as I might have.’

Reputation intact, surely it was one of the lowest points of his career, I ask? ‘You could consider that or any number of things,’ he says, quickly changing the subject.

During his five and a half years as Commissioner he’s achieved a lot of his aims (‘in partnership with 44,999 others’), but not as quickly as he’d have liked. He has turned the Met from a force into a courteous ‘service’. Now he’s been offered ‘one or two’ non-executive directorships, involvement with security firms and invitations to lecture and write a book. He will also be playing bad bridge, coarse golf and ‘boring’ people with talk about his grandchildren (as his Who’s Who entry testifies). His heart attack, he says, made a vast difference to his life. ‘The stresses and strains of this job are an enormous burden if you literally take them to heart. I think I did. I care about this job. It consumes my whole being.’

He wrings his hands and comes across as gentle, but there’s a steeliness in his eyes which seems at odds with his open, friendly manner. Known for being calm and approachable, he admits: ‘My toughness is hidden beneath that genial exterior.’

Before the heart attack, he worked 16 hours a day – now it’s 13. ‘The first week off was almost a luxury, if it hadn’t been for the worry of whether I was going to get over it. I didn’t really feel frightened that I was going to die, but I was concerned about the things that I hadn’t done. ‘I haven’t really been fair to my family and owed it to them to spend more time with them. I’ve not wholly succeeded in that. I also knew I needed to learn to delegate and share responsibilities.’ Although his lifestyle might have cost him his life, he believes it has been worth it and his family has been supportive.

He met his wife Iris (they have been married for 36 years) when he was on the beat in central London. ‘I first saw her when I looked through the window of the hospital in Great Ormond Street and saw these rather good-looking nurses. Coincidentally, I then met her at a police dancing class. I thought she was very desirable.’ He used to stop the traffic to allow her to cross the road.

Iris has provided ‘great stability’ in his life. She’s worked in jobs that have allowed her to move and support her husband according to his placements. ‘It’s been,’ he says, ‘a very satisfactory, fulfilling marriage.’

Communication and understanding are the secrets of their successful relationship. ‘One is also tempted to say ‘love’, but what does that mean? At first it’s very passionate and then it becomes part of that stability, of being able to discuss things and enjoy similar interests.

‘I used to think I was passionate, but my wife may disagree. I believe I’m a romantic, but she doesn’t think so. Occasionally I buy her flowers.’ HE WAS brought up with a strong work ethic. Born the fifth of seven children into a poor working-class family, Sir Peter was the son of a bankrupt farmer.

‘From an early age I knew I had to earn my living. To achieve anything in this life, you’ve got to work.’ Aged six, he helped collect pigs’ swill; aged seven, he weeded gardens and delivered newspapers. ‘I had to finish early on Sundays to go to church three times. My parents insisted … I can’t really remember having holidays as a boy.’

He was an energetic, inventive child, and a comic and hooligan – he was once caught by the local bobby three times in one afternoon for different bike offences. (He once visited Associated Newspapers for an executive lunch. Asked whether he’d like to see anything – like the news room – he declined, requesting instead to ride up and down in the glass lifts.) His family’s size taught him to get on with people. ‘I was at constant war with my siblings. I learned that you don’t win arguments by resorting to violence or aggression.’

He left school at the age of 16. ‘My parents couldn’t afford to go on feeding an extra mouth. I remember seeing my mother crying because she hadn’t got enough money to feed the family.’ He worked for £1 a week at the local town clerk’s office ‘hoping to become the youngest town clerk in the country’.

He regrets his lack of university education. ‘I went to evening classes to learn shorthand, Russian, French and German.’ He has an orderly mind, listens attentively, and chooses his words carefully. He’s a slick and cunning communicator.

So what of his own children? He has three and says he is very proud of them – ‘not because of what they’ve achieved, but for their independence of thought’ – and seems reasonably satisfied with his role as a father. His son markets security devices, one daughter is a health visitor, and the other is a fashion graduate who helps disadvantaged youths and does cleaning two days a week.

‘I think I made a loving father. I hope so. I wasn’t there as much as I could have been in their formative years. I was spending too much time sorting out other people’s problems on the anti-terrorist squad. I know my son needed his father at that time, and I wasn’t there enough. ‘At times I was firm. I disciplined by example. I did slap them, but I was only once close to giving my son physical admonishment – pushing him up into his bedroom and giving him a jolly good hiding.

‘He’d stolen some money from us and then refused to admit it. It couldn’t have been anyone else. It wasn’t that he’d done it, but the fact that he was prepared to let someone else take the blame. I became furious with him. He’d wanted to keep up with his peer group and buy cigarettes.’

AS A child Sir Peter thought of becoming an agricultural auctioneer, selling cows and sheep in a market; he also thought of being a stage conjurer and comedian. ‘Some people say I’ve achieved one of those. I’m not going to say which.’

He leaves his job with mixed feelings. ‘I’ll miss the camaraderie and being involved in high-level decisions.’ The motto he’s going to put on his coat of arms is ‘adversity to advantage’. It’s a measure of what he’s achieved.