London bombers: single team, moderate local knowledge, and missed targets
Here is the tube map.
The bomber was working Circle line, pivoting around King's Cross. They took a train east, left a package timed for Liverpool Street, came back, sent a bomb on west out of King's Cross - and I bet it was intended for Paddington. Edgware Road makes little sense as a target, train was probably a minute or two late. They then dropped one on the Piccadilly Line and got out.
The bus bomb was either a mistake - they couldn't get back on the tube, or it detonated early (in which case forensics is about to blow the case and ID the bomber team) - or they realised the tube was shutting down and they abandoned the bomb and walked away. May be worth looking for two people taking a taxi near a bus stop "down route" from the bus around 9:30.
A well planned attack would have sent the fourth bomb to Victoria or Waterloo, but that is hard to make before everything shuts down, which is why I think they just left it and walked away. This was planned, but not incredibly well planned. I wish "terrorism pundits" on the telly would stop perpetuating the Myth of the Hypercompetent terrorist. It was probably two slightly nervous men in their mid 20s with one or two older men assisting the preparation and planning and resources from the outside through mail drops.
Other big question is whether explosive were commercial and stolen, or military and from a foreign source - and either way, whether they were tagged and therefore traceable.