The latest instalment of Sir Ian Blair’s memoirs, Policing Controversy, is published in the Mail on Sunday today. Inevitably the controversy surrounding his removal as Commissioner by Boris Johnson tends to focus on the constitutional issues and the question of the politicisation of the police.

Yet Blair’s autobiography also shows that Boris Johnson clearly privately admitted what his supporters still refuse to do publicly – that under Ken Livingstone London was achieving real results in the fight against crime. Boris Johnson had to tell the opposite story in order to whip up hysteria about crime during the election but he knew perfectly well that the real story was a good one.

Here is what Blair reports.

‘You will have to praise the achievements of the cops where praise is due,’ I said [to Boris Johnson]. ‘You cannot go on talking down the fall in crime in London, which they have achieved. They need to know you care about them. That way we can work together.’

He looked me straight in the face and replied: ‘I agree. Look, I know that Ken, the Met and you, in particular, have a good story to tell about crime in London in these last few years but I simply would not have been elected Mayor of London if I had admitted that.’

Sir Ian adds: “I understand that politics is the art of the possible but the complete shamelessness of that comment was pretty staggering.”

This ought to be highly embarrassing for Johnson, though most of the press will probably ignore it, given that the current dynamic of most of the media is to leave the Conservatives alone whilst going after Labour.

Of course a considerable proportion of the media shared and promoted Boris Johnson’s attempt to talk down the achievements of the Met during Ken Livingstone’s period as mayor, which were delivered through adequate funding for the police, the highest number of police officers in the city’s history, and the introduction of neighbourhood policing. Though Johnson talked the talk on crime he is in fact presiding over the first real-terms cuts in the police budget since the mayoralty was created.

One of the things London needs is a mayor who will set out what the real issues for London actually are, in order to work out what London’s requirements are.   Johnson is not interested in that: hence the nonsensical waste of removing articulated buses in favour of vehicles with less capacity at a higher cost, the abolition of the western extension of the congestion charge zone even though it will both increase traffic levels and cut revenue, and the hammering of public transport fare payers.

His handling of the crime debate, underscored by Blair’s new book, is another example of that. He wanted to build up myths and hysteria and talk London down, regardless of the work of police officers on the ground.

But, even if Boris Johnson won’t do it, that’s what London needs – a mayor who will be straight about the issues facing the city and who will be serious about taking the objectively right decisions.

Thanks to Blair’s memoirs, Boris Johnson now has the problem that every time he denigrates the record of his predecessor, it will be possible to point to his own admission to the Police Commissioner that under Ken Livingstone the record was a good one.