"We continuously monitor the effectiveness of, in particular, the liquid security measures..."

How, one might ask? But hold on:

"The fact that there has not been a serious incident involving liquid explosives indicates, I would have thought, that the measures that we have put in place so far have been very effective."

Ah, that's how. On which basis the measures against asteroid strike, alien invasion and unexplained nationwide floods of deadly boiling custard have also been remarkably effective.