Somewhat perplexed, Moist said, ‘It looks like a children’s plaything, sir.’

‘In fact it is a very well crafted model of something much bigger and far more dangerous.’ Lord Vetinari raised his voice and said, as if talking not only to Moist but to the world in general, ‘Some might say that it would have been easy for me to prevent this happening. A stiletto sliding quietly here, a potion dropped into a wine glass there, many problems solved at one stroke. Diplomacy, as it were, on the sharp end, regrettably unfortunate, of course, but not subject to argument.

‘People might say that I wasn’t paying attention and through neglect of my duties allowed the poison to seep into the imagination of the world and change it irrevocably. Perhaps I could have taken some action when I first saw Leonard of Quirm doodle something very much like this little toy in the margins of his drawing of the “Countess Quatro Fromaggio at her Toilette”, but of course I would rather shatter the most priceless antique vase than see any harm come to one hair on that most useful and venerable head. I thought it would go the way of his flying machines, nothing more than a toy.

‘And now it has come to this. One simply cannot trust the artificers; they design some terrible things for the sheer love of doing so, without wisdom, foresight or responsibility, and frankly, I would like to see them chained up where they can do no harm.’

And here Lord Vetinari paused and added, ‘And I could have made that happen in an instant were it not for the fact, Mr Lipwig, that the wretches are so damn useful.’

He sighed, causing Moist to worry. Moist had never seen his lordship so discomfited, staring intently at the little truck as it went round and round on its little rails and filled the room with a smell of methylated spirits. There was something hypnotic about it, for Lord Vetinari, at least.

A silent hand dropped lightly, and eerily, on to Moist’s shoulder. He turned around quickly and behind him was Drumknott, smiling gently.

‘I suggest you pretend you didn’t hear anything, Mister Lipwig,’ he whispered. ‘It’s the best way, especially when he has one of his, er, sombre moments …’ Still whispering, Drumknott continued, ‘A lot of this is to do with the crossword, of course. You know how he is about that. I intend personally to write to the editor. His lordship considers elegant completion to be a test of his integrity. A crossword is meant to be an engaging and educational puzzle.’

And then, his normally pink face reddening, Drumknott added, ‘I’m sure it’s not intended to be a form of torture, and I’m certain that there is no such word as lagniappe. However, his lordship has terrific powers of recovery, and if you care to wait while I make you some coffee I’d wager he’ll be his old self again before you can say “death warrant”.’