Date: the morning of July 7, 2005. There has been a series of mysterious explosions on Tube trains in the capital, which London Underground - and the police - have put down to electrical power surges. This analysis is suddenly revised when a bus explodes outside Russell Square station. Inside Scotland Yard, Brian Paddick, the deputy assistant commissioner, displays the acuity and deductive prowess for which the British police are world famous: “You don't get power surges on a bus,” he tells a colleague.

The assembled top rozzers realise that bombs are going off all over the place, London is under attack and, in this moment of dawning crisis, they coalesce around a set of priorities. Or at least, they write down on a piece of paper what their priorities are and then give it to some woman to type up - saving lives, treating casualties, trying to catch the bombers etc. That sort of thing. And then themselves follow a rather different set of priorities that they haven't written down. DAC Paddick hotfoots it to the press room and tells the Met's media monkey: “I'll be your talking head.”

Paddick and a press officer then run off to Commissioner Ian Blair's office to tell him this important news. “Brian is going to do the media.”

The commissioner replied: “No, he's not, I'm doing it.” (Paddick's italics). There's a squabble, for a bit. Then the commissioner's staff officer (someone called Moir Stewart, definitely not Moira Stewart) bursts in with a message just received from Cabinet Office Briefing Room A (Cobra). “The commissioner is not to do the media.”

To which Blair replies: “Tell Cobra I'm doing it.”

There's some more squabbling about who is doing the media, and then some negotiations between Paddick, the press office, Blair and his lackeys. Eventually it is agreed Blair should do the first round of interviews and then Paddick will take over. That way, everyone gets to feel really important. There are then some discussions about the stuff they should tell the media and the things they should leave out.

Despite his early protestations in this entertaining and revealing autobiography, I do not think that Paddick likes Ian Blair much. And while the two men can be viewed as allies in this new-fangled liberal policing, with its emphasis upon hate crimes, and not smacking miscreants around the head too hard etc, they could not be more different. Paddick is almost painfully earnest; naive on occasions, utterly unable to dissemble, candid and honest - he was nicknamed “Peter Perfect” by other officers when he started out, and was greatly mistrusted by many of the rank and file. The Blair that comes across in this book, meanwhile, is much as you may have gathered from his almost endless television appearances; blankly arrogant, a political animal to the point of downright deviousness, vain and unimaginative. I know who I would prefer to have running the Metropolitan Police, and find it vaguely shocking that Blair is still entrusted with the task; so, I suspect from reading this book, does Paddick.

The two men fell out, finally, over the commissioner's repeated testimony to the media that he had not known (for 24 hours) that the Jean Charles de Menezes who had been shot dead by his officers on a Tube train at Stockwell in 2005 was an entirely innocent civilian and not a deranged Muslim terrorist. Paddick did not believe Blair and nor do I. But maybe we're both wrong about that. Elsewhere, Paddick snipes at Blair's blatant and base pursuit of political patronage, and even at the manner in which he redecorated his office (at great expense to the taxpayer) so that it “looked and smelt like a DFS showroom”.

Paddick, meanwhile (despite being the scourge of our tabloid newspapers, drug-friendly poofter, the odd copper, and so on), has the word “sensible” stamped through him. But although not notably academic, he has a certain intellectual bravery; his strategic reports and investigations often reached conclusions that ran against the prevailing political fashions, and were shelved for that reason.

His alleged “soft” stance on cannabis, which first brought him to public prominence, was never the consequence of a libertarian ideology, but, again, based on a common-sense approach to policing in Brixton, where he became one of the few policemen to acquire the trust of the black community. He still seems a little surprised that his “legalise it” stance aroused such virulent hostility, which is perhaps another example of Paddick as political innocent.

Elsewhere, we join him on his early beats on the street with fellow officers who wished to emulate The Sweeney and were sometimes possessed of views that might not accord with those of, say, Dr Martin Luther King. Paddick was, as ever, regarded with dark suspicion. The sheer paucity of academic brilliance in the Metropolitan Police is evidenced by the early appointment of the young Paddick to a planning role, because he was the only copper within miles who had a maths O-level. He also gives us an insight into his once troubled and now reconciled sexuality, and the scathing homophobia he suffered (largely, it has to be said, from his mum).

He is now standing as the Liberal Democrat candidate for the post of mayor of London, of course. I do not think he is sufficiently astute or devious to take many votes off those old bruisers Ken Livingstone and Boris Johnson; however, on the evidence of this book, London could do a lot worse.

Line of Fire: The Autobiography of Britain's Most Controversial Policeman by Brian Paddick with Kris Hollington

Simon & Schuster £17.99 pp341

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