A student from a wealthy family was arrested yesterday after a fire extinguisher was hurled from the roof of Tory headquarters during Wednesday’s riots.

It crashed to the ground inches from policemen who said they would almost certainly have been killed if it had struck them.

The extinguisher was thrown from the roof of 30 Millbank after a peaceful student protest was hijacked by anarchists. Video footage showed the canister apparently being launched over the edge by a protester.