I think, when all is said and done, that the body count was low compared to what it could have been (FoxNews now claims that they found two unexploded bombs) Considering it has a population of seven and a half million, the casualties seem thankfully low.
From the Belmont Club
From the amount of damage caused, the explosive devices used appear to have been in the tens, rather than the hundreds of pounds. This is good news. It also means that the enemy has not grown in overall capability since the days of 9/11 and 3/11.
I wonder if the time was selected to coincide with the G-8 meetings, presumably a lot of the British security people would be concerned with that this week.