Obama told a joke and Brown laughed… and laughed… and laughed… and laughed
Mr Obama uttered a sentence. Mr Brown nodded. Mr Obama paused. Mr Brown froze, frowning. Mr Obama made a very slight joke.
Mr Brown gassed himself, laughing for a good 30 seconds, eyelids fluttering like the wings of a soft-flapping Cabbage White.
Outside, in the road off Whitehall and in the great court of the Foreign Office, I counted 24 Range Rovers, all of them pretty brand spanking new.
Before Messrs Brown and Obama entered the room where we had been cooped up for two hours, flunkeys and bit-part players came slinking in, David Miliband and Hillary Clinton among them.
What an odd duo Mrs Clinton and the boy Milipede make. She looks like a mother taking her teenage son round a university campus on Open Day.