David Cameron 'corruption' remarks: If you can’t say something nice, Prime Minister...

It’s all right, though, because, as Number 10 has pointed out, the presidents of Afghanistan and Nigeria readily acknowledge the problem of corruption in their own countries

David Cameron (second right) in conversation with (from left) Commons Speaker John Bercow, the Queen, the Archbishop of Canterbury and Chris Grayling

No guide to modern etiquette gives precise instructions on what to do when making small talk with the Queen and the Archbishop of Canterbury at the same time. We imagine if it did, it might suggest keeping it light, certainly non-controversial at least – especially if there are TV cameras pointing straight at you and microphones hovering.

In the Prime Minister’s defence, the stakes were high: that much is clear from the pictures. Anything too dull and you risk the archbish and her maj pretending to need the loo and never coming back, and that’s going to leave you dragging the conversational nails down the blackboard with Grayling and Bercow, the toilet escape route firmly blocked by church and crown.

But those prospective awks will be as nothing when Afghanistan’s Ashraf Ghani and Nigeria’s Muhammadu Buhari arrive for the anti-corruption summit, the entire world having overheard them being the subject of Buckingham Palace based small talk about “the two most corrupt countries in the world“.

And not just corrupt – fantastically corrupt. “We’ve got some leaders of some fantastically corrupt countries coming,” Cameron breezily informs the Archbishop. Fantastic. Not the most obvious corruption adverb, that.

It’s all right, though, because, as Number 10 has pointed out, both men readily acknowledge the problem of corruption in their own countries. Which means that when, some time later in the week, the Nigerian President is inevitably caught on camera joking about just how much weight David Cameron has put on since the election, being merely factual, that will be fine too.