What's behind the spike in crime in the capital? London awakes to another stabbing, this time of a man in his early 20s in Hackney.

One reason why the debate is politically fraught for Theresa May is that for some, the explanation requires just three words: stop and search, which the PM restricted the use of as Home Secretary. That opinion is well-represented on the right but Labour's David Blunkett has also added his voice to those blaming the rise in knife crime on the change.

Theresa May's former bearded chief of staff turned Theresa May's clean-shaven outrider, Nick Timothy, defends his former boss in his Telegraph column today. The problem isn't clamping down on stop and search but the failure of the Mayor of London, Sadiq Khan, and Metropolitan police chief Cressida Dick to come up with a proper strategy to fight crime: such as the one they have in New York, which has seen its crime rates plummet.

Who's right? Well, the first thing to note is that for all the talk about what the United Kingdom in general and London in particular can learn from New York, what has actually happened is that New York's eyewateringly high crime rate has fallen to meet London, rather than the other way round. It's also worth noting that the recent spike may just turn out to be statistical noise and that at the end of the year the capital's murder rate might look a lot like last year's, and the year before that. On top of that, there was a increase in stabbings in London in 2011 that turned out not to augur any reversal in the prolonged fall in violent crime in the United Kingdom (and indeed in the western world).

But let's say that the increase is real and sustained: what could be behind it? I looked at the numbers and it is hard to support the claim that clamping down on the illegal use of stop and search is part of the problem. The number of arrests after stops hasn't gone down in real terms – what has fallen is the number of people being searched for no good reason.

But the biggest problem with pinning the blame on Theresa May's decision to cut down on stop and search is also the problem with Nick Timothy's attempt to blame Cressida Dick and Sadiq Khan: the use of stop and search has fallen most significantly in London. But the increase in crime in London isn't an isolated one: as Anoosh notes here, knife crime outside London is up by 21 per cent – inside London it is up by 23 per cent. (And these small percentage differences are actually even smaller in terms of actual incidents.)

So any debate about crime in the capital has to start by acknowledging two things: the first is that a lot of the talk about a rise in crime may turn out to be misplaced by the end of the year. The second is that any explanation of what's going on in the capital has to also explain what's going on outside it. Whether the argument being made by Labour and the Police Federation that years of spending restraint are starting to show, they do at least have the benefit of actually tackling that problem rather than in engaging in old fantasies about stop and search and police power.