If so, the bomb maker screwed up bad. Fortunately for all concerned, except him.
Yep the bomb maker shouldn't worry about Scotland Yard, as much as he should worry about his superiors finding him.
Having spent 6+ years in the USAF as a weapons specialist (IYAAYAS), I know a bit about explosives and weapons. If I witnessed a bombing I would help the injured. If I witnessed strange sounding low-order explosion, more like a thump than a bang, I would run upwind as fast as I could for as long as I could. Low-order explosions are THE way to spread bio/chem weapons. I don't think that is the case in London, it sounds more like bad bomb making to me.