It's intense, the way in which Harry descends on Philip. Hard, without mercy.

The flare strikes and hits the ground, smoke and intense light exploding in the small space.

It might be more effective if his assailant weren't in full protective gear. If he weren't able to breathe, if the light blinded him. But he is wearing a suit designed to protect against something very like a flare going off and so it does little damage.

It does, however, create a great cloud of smoke and roaring sparks.

All the better to hide in. To lunge for the pick axe and scramble back to locate where his victim has gone.