London bombs - where did they get the explosives?

Where did the London bombers get their explosives?

One of the ways to fight terrorists is to stop them getting their hands on explosive materials. During the fight against the IRA the UK was very effective at doing this, so that the IRA was reduced to using bombs made from fertilisers. These are large, comparatively weak and difficult to move around.

The London bombers were clearly not using fertiliser bombs but had something much more effective. In the aftermath of the Iraq invasion the Americans very stupidly allowed somebody to make off with 380 tons of military explosive from a dump at Al Qaqaa. None of that has been recovered and is presumably in the hands of terrorists.

Are we seeing the first consequences of the Al Qaqaa blunder?