Comment: at last, concrete proof that Livingstone's sums are wrong

It has regularly been the voters' top priority - and may help to explain the Tories' poll lead. Along with trust, crime is the only major issue where Boris Johnson consistently outscores Ken Livingstone.

At first sight, Ken's deficit in this department is puzzling. According to the figures for police-recorded crime, there has been a reasonably clear drop in most crime under him. Murder is down by 12 per cent since he was elected in 2000, rape by eight per cent, and total crime by 13 per cent. He boasted only yesterday that the fall in crime was "accelerating," with the figures showing crime down

5.5 per cent a year on average.

The problem for Mr Livingstone is that nobody believes the figures. At almost every election hustings, someone in the audience, or one of the other candidates, has listened to the Mayor's blizzard of statistics and quietly said: "Yes, but we don't feel safer."

Until now, nobody has had concrete proof that their feelings are right and Mr Livingstone's, and the police's, numbers are not all they seem.

Now, with this shocking Metropolitan Police Authority report, we have that proof.

The report reveals, in considerable detail, the many strokes pulled by under-pressure police officers to make the numbers look better - like reclassifying some serious crimes, such as robbery, into less serious crimes, such as theft.

Or even, extraordinarily, preventing victims from reporting crimes at all through various dodges such as requiring them to give a 15-digit number before they can file a report.

Until now, Mr Livingstone has been able to blame the media for the public's fear of crime. Until now, he has been able to dismiss the British Crime Survey, the other main measure of crime, which shows that crime in London, after falling a few years ago, is currently static or even rising. The Mayor has called the survey "a giant opinion poll" which reflects public perception as much as the reality. But it is not an opinion poll, it is a survey which asks people whether they themselves have experienced a crime and now seems as close, or closer, to the reality - and less susceptible to fiddling than the police numbers.

In truth, there almost certainly has been a drop in crime (with some nasty exceptions, such as the killings of teenagers).

You might be able to fake some figures but you can't fake them all and you can't entirely fake a trend as pronounced as the reduction we've seen in London over the last 15 years.

But what is clear is that some police recorded crime figures are, in the words of the MPA, "dishonest" and "inaccurate".

That makes them a hopelessly frail basis for the Mayor to claim a policing triumph. What seems clear, too, is that the "acceleration" in the fall in crime hyped by Mr Livingstone may be a factor as much of statistical manipulation as anything else.