As my regular readers will know, I'm not a great fan of Ken Livingstone.
However he has probably delivered a knockout blow to Tory Shadow Home Secretary Chris Grayling on a Newsnight discussion about the inadvertent leak of sensitive information by the Assistant Commissioner, and head of counter terrorism, Bob Quick.
It is a joy to watch. So get to iPlayer and watch it again (as soon as it appears there). And someone with more technical know-how than me put it on YouTube so everyone can see it.
The killing blow was leaving Grayling spluttering and unable to answer the charge that only Al-Quaida would be happy with his position on the the leak.
This isn't cheap jibes about second home allowances. This went to the heart of who do you trust to run the country.
Future Home Secretary? Not any more.