Having watched Cummings in front of a select committee, I reckon the chance of him making a success of this statement and Q&A, and avoiding further damage to the PM, are vanishingly low. Johnson is mad to allow it.

There's a real risk he'll say or do something completely bonkers, and come across angrier and worse than Trump. Even if he resigns, he's quite likely to wound Johnson badly as he goes. Johnson is mad to allow it.

Is Johnson really such a fool that he trusts Cummings to stick to an agreed line? Can't he see the danger that Cummings might use this to satisfy some need of his own? He's putting his premiership in Cummings's hands today. As I keep saying, he's mad to allow it.

Finally, unless someone is tasked with physically ejecting Cummings and journalists at a certain time, there must be a risk this event turns out to be not only absurd but uncomfortably long for Johnson.