If we only knew where to drop the bomb, we would have done it already.
It may be too early to know, but just how bad is the damage to the tube? You said:
This takes out most public transport in London in one fell swoop.
Do you mean days, weeks, months, or longer before the trains run again?
Public transport is running again this morning; yes there are alterations and delays in the schedule, and bus replacement services are taking the place of the London Underground in certain places, but London is resilient and getting right back to work.
Regards, Ivan