It's been tried, sometimes successfully, sometimes less so. If you happen to have your own squadron of bombers, chances are you could take out thousands of us and ease the traffic chaos, yeah. Of course, everyone who didn't die would come and kick you to death with spiky shoes, so - your call. :o)
People who want to destroy London - and there are some, evidently - need to realise that it's bigger, older and uglier than they are, and it punches back. Individuals may die. Indeed, individuals HAVE died, from the days of the Blitz to the IRA attacks, to this latest lot of backpack-wielding suicidal ponces. I would never dream of making light of their deaths. But to kill handfuls of Londoners only makes the idea, the spirit of London stronger. So I guess the ultimate answer to this question is: Come and have a go if you think you're hard enough!