Still staring down at the city, Lord Vetinari said, ‘My dear Mister Lipwig, you are clever and certainly smart but you have yet to find the virtue of wisdom, and wisdom tells a powerful prince that firstly he shouldn’t put just anyone he likes in prison, because that is where he puts the people he doesn’t like, and secondly that mere unthinking dislike of something, someone, or some situation is no mandate for drastic action. Therefore, while I have given you permission to continue, the train does not have my wholehearted approval. Neither does it have my curse.’ The Patrician seemed to consider for a moment and added, ‘Yet.’

He walked up and down again for a second or two and then, as if the thought had only just struck him, said, ‘Mister Lipwig, do you think it a possibility that a train could in fact get all the way to, say, Uberwald? That journey is not only extremely slow, tedious and uncomfortable by coach, but it is fraught with many … ah, perils … and traps for the unwary traveller.’ He paused and added, ‘And indeed the unlucky bandit.’

‘Oh, yes, that’s where Lady Margolotta lives, isn’t it, sir?’ said Moist breezily. ‘But it would mean negotiating the Wilinus Pass, sir. Very dangerous up there! Bandits have been known to knock out coaches by throwing down rocks from the crags.’

‘But there is no other way without a very lengthy detour, Mister Lipwig, as you probably know.’

‘In that case, my lord … I think it might be possible to construct such a thing as an armoured train,’ said Moist, inventing furiously. He was gratified to see that Lord Vetinari brightened when he heard that, repeating the words ‘armoured train’ once or twice more.

Then his lordship said, ‘Can it really be possible?’

And in the squirrel cage of Moist’s mind, he thought, Can it? Can it really? It must be more than twelve hundred miles! It takes well over two weeks by coach and that’s if you don’t get hijacked, but who was going to try to hijack an armoured train? The engine would be wanting water frequently and is it possible that it could carry enough coal for the whole journey? The numbers rolled in his head. Stopping places, troughs for water, mountains, gorges, bridges, marsh land … So many things, any one of which could scupper the project …

But going to Uberwald would mean passing through so many other places on the way and all of them could be opportunities to make money. The demons of critical path analysis swarmed around his brain. There was always something that you had to do before you could do the thing you wanted to do and even then you might get it wrong.