Eh, I think the media over there's just looking for something to report. Not much really exciting happening nowadays, unless of course, Obama gets stabbed. (a symbolic meaning in that, too, a cookie to who gets it)
I mean, that's what I've surmised from what I've read and heard about the British news media. I've never personally read the Guardian or watched a BBCNews broadcast unfiltered in England.
But, most definitely, crime is an issue, I mean, it could just be a slight increase of crime, and since it involves knives, which everyone fears and the media loves to capitalize on, it gets brought up and everyone starts talking. Of course the politicians are going to discuss it; they're being asked the same questions by the people, and the need to keep the pressure off.
As for the private-sector, biased, filtered, controlled media here in America....
Fox News? the only reason that station is up and running is because 70% of this country consists of rednecks who can't make educated decisions, so they turn to the first person that sounds like them, looks like them, and have one or two thoughts in common. The thoughts on the redneck's side would be small bits and pieces of political theory processed and garbled like a bad game a of telephone and then picked up by a sycophant.
CNN? Well, they claim to be an unbiased, trustworthy news source. They kinda achieve that 'goal'. Most of their reporting tends to be more Independent, but as with all of the Big 3 news outlets, you can't verify if they're telling the whole truth or if that 'truth' is the truth without going out there or marauding through Google, looking for blogs owned by smart people.
MSNBC? Hmm... the second-most funny news outlet. Keith Olbermann and O'Reilly have been feuding for a while now, their ideologies colliding perpetually, and Olbermann naming O'Reilly 'Worst Person of the Week', generally along with Sean Hannity or Rush Limbaugh in the Worst Person segment of his show. Generally speaking, you'll find NBC's networks, including MSNBC, to have a bit of a liberal taste to them, although not as far gone as Fox.
But I digress,
The main point here (aside from the explanation of the American news outlets) is that crime's just an issue in all major cities, conversely, crime in New York is in a downward trent. But both cities are targets of great value. It might be boredom, it could be the knifings themselves, but I doubt that London's streets will be running with blood. If so, I think the SAS would find themselves well-employed here, but I'm not sure if there's a National Guard system in the UK like there is here in the states.