Bring in the army, I bet there's quite a few squaddies champing at the bit to see to these little twats! Give the army the water cannons loaded with this smartwater stuff, we'd know who they are then days after......Rubber bullets, when they run out of them I hear that AAA batteries fit the guns too.
Those that have already been arrested won't be in the least bit worried as all that will be done is to pat them on the shoulder, tell em "there there" and send em on a weeks holiday in spain, personally, I think they should all have their benefits stopped till the repairs are paid for, The smartwater will help to identify those giulty!
Mr Cameron can save himself the journey of coming back of his hols....he'll do f**k all to stop it anyway!