Cameron's deal to trade Speakers with Kabul
By their deeds, ye shall know them.
You can often tell what people - and politicians - are thinking not by what they say but by what they do.
Take for example David Cameron. Today in Kabul he announced a package of measures to improve Afghanistan's democratic institutions.
There will be lots of "shared best practice" and other ghastly bureaucratese. But crucially there will be an exchange programme for the Speakers of the British and the Afghan parliaments.
In other words, the prime minister has condemned Commons Speaker John Bercow to many long flights to Kabul.
It is not quite exile but I can imagine the wry smile creeping across the Downing Street face as he signed off on that one.
Note to Speaker: Don't interrupt the prime minister too often in the Commons. He can do more to you than you can do to him.
Take too the Union Flag flying behind Mr Cameron at his press conference with Hamid Karzai at the presidential palace.
The soldier standing guard over the pole wiped his nose on the flag several times. The flag was also flying upside down.
Now you could think: Who cares, apart from my old teacher and the sort of people who write letters to the Daily Telegraph? There are certainly more important things to worry about.
But it was a gentle reminder of Britain's place in the world, that Mr Cameron is just another foreign leader passing through. This afternoon, no doubt, the president's guards will perhaps be getting another flag wrong for another travelling dignitary arriving to tell them how to live their lives.
And as for Mr Cameron himself, he revealed his true thinking not just by his words at the press conference but in the way that he presented them.
He said there were three questions: Why are British troops still here? How will the mission be completed? And what will Britain's long term relationship with Afghanistan?
All fair enough. But he also said, right at the top, that these were not his questions but those of the British public back home. The gradual withdrawal of British forces may be 'conditions based' and dependent on the growth and improvement of the Afghan army, but it is driven above all by David Cameron's sense that the British public have got fed up with Afghanistan and they want out.