London has had more than it's fair share of bombing in the past.

The Nazis bombed London around the clock for nearly a whole year. Hundreds of bombs every 24 hours during the blitz. Not to mention the deadly rockets Hitler developed to fire on London from occupied Holland. Rockets that took out entire blocks in one explosion.

And more recently, the IRA bombed a lot of major cities in the UK.

In the grand scale of things, the British people have seen a lot worse attacks.

Agreed Cliff,
Gonna take a bit more to make us worried.