Lord Vetinari broke his silence. ‘Certainly, Sir Harry, and perhaps in the meantime someone could locate my secretary?’

They turned to look at the engine, which had come to a stop in a kind of human way, not all at once, but settling down like an old lady making herself comfortable in a favourite armchair, except that at that moment Iron Girder blew out a hissing stream of shining water vapour, which does not normally happen with old ladies, at least not in public.

Drumknott, up in the cabin, was still desperately pulling the chain for the next whistle, and he seemed to be weeping like a toddler bereft of a favourite toy as the sizzling got fainter. He caught their gaze, carefully relinquished the chain, climbed down from the footplate and almost tiptoed through the sizzling steam and the occasional unexpected mechanical creak, as the metal cooled. He walked gingerly over to Dick Simnel and said, hoarsely, ‘Could we do that again, please?’

Moist watched the Patrician’s face. Vetinari seemed to be deep in thought, then he said breezily, ‘Very well done, Mister Simnel, an excellent demonstration! Am I to believe that many passengers and tons of freight could be carried by means of this … thing?’

‘Well, yes sir, I see no reason why not, sir, although of course there would have to be some additional work, decent suspension, and properly upholstered seats. I’m sure we could outdo the stage coaches, which are a right pain in the arse, sir, and no mistake … if you would excuse my Klatchian.’

‘Indeed I will, Mister Simnel. The state of our roads and therefore of our horse-drawn carriages leaves much to be desired. A journey to Uberwald is a penance without a cause and no amount of cushions seem to help.’

‘Yes, my lord, and riding on sleek steel rails in a well-sprung carriage would be the height of comfort. So smooth!’ said Moist. ‘Perhaps people could even sleep in a suitable carriage, if there was such a thing?’ he added. He was surprised that he’d said this out loud, but, after all, he was a man who saw possibilities, and now he was seeing them in spades. And he saw the face of Lord Vetinari brighten considerably. Iron Girder had ridden her tracks much better than the post horses managed with the flints and potholes of the high roads. No horses, thought Moist, nothing to get tired, nothing that needs feeding, just coal and water, and Iron Girder had pulled tons of weight without a groan.

And as Harry led the Patrician towards his office, Moist ran his hand over the warm living metal of Iron Girder. This is going to be the wonder of the age, he thought. I can smell it! Earth, air, fire and water. All of the elements. Here is magic, without wizards! I must have done something good to be in this place, here today, at this time. Iron Girder gave a final hiss, and Moist hurried after the others heading for their lunch and the future of steam.