[Pierre]

The concern is that compared to recent Radical Islamic attacks this was a sophisticated nail bomb. To construct one is tricky and to construct a stable one that goes off when you want it to is even trickier and takes some skill.

This begs three questions.

1. Did the bomber build the bomb? Well let's hope so, now he's dead.
2. Was the bomb built o/s the UK and shipped in? - you would expect not.
3. Did someone else in the UK build the bomb and give it to the attacker? This is the worst option, this means there is a person with sophisticated bomb making skills in the UK, which would suggest and organised IS sympathetic cell in the UK.