And when Moist came back to the guard’s van after pacing the corridors and gave the not very secret knock, he found the door opened by Nobby Nobbs, a watchman who though technically human (with a certificate to prove it) was so much like a goblin that he had acquired a goblin girlfriend. Adora Belle had met her many times and she had told Moist that Shine of the Rainbow was throwing herself away on Nobby.

‘Wotcher, Mister Lipwig. You should have been ’ere when Mister Vimes was interrogating that old suspect. He rolled up his sleeve and the dwarf went mental, and I mean proper mental. He saw that mark, you know, the one on the commander’s wrist, and went, well, totally mental, promising absolutely everything. Never seen anyone so scared in all my life and Vimesy hadn’t even touched him. He broke, sir, that’s the only way I can put it. He broke. I mean, he’s had a go at me on occasions, you know, about such things as what I found on the street and was hurrying to give back to their owner and suchlike. Nothing important. But that dwarf … it was like he melted, sir. Melted! You wouldn’t know Done It Duncan, not being in the Watch, sir, well, the poor bugger owns up to anything just to get a drink and a place to sleep in the cells and maybe a chat and a ham sandwich. But this lawn ornament, he’s got it worse.’

Moist looked around. ‘Where are they now?’

‘In there. And Mister Vimes took the young ’un off somewhere else with Fred.’ Nobby pointed towards the far end of the guard’s van. ‘Mister Lipwig, you know that great idea you had?’

Moist hesitated. ‘Help me, Nobby, I have a lot of great ideas.’

‘Right, sir – the one about sorting the mail on the train, sir?’

And Moist thought, oh yes, and it would work. But Nobby carried on. ‘Well, there’s a special carriage on this train. It has shelves and pigeon holes and everything.’

Inside the mail carriage Moist saw the commander and his new little friend, with Fred Colon. Vimes was talking quite cheerfully to the young dwarf and when he saw Moist he gave a quick gesture indicating that he could listen but shouldn’t disturb the delicate process. There were no signs of fighting or nastiness of any kind and there were two cups of coffee nestling in the wire pigeon holes. The commander, as soothingly as a mother with a new baby, played a theme that put Moist von Lipwig, confidence trickster, liar, cheat, fraud, swindler and king of slyness, the sort that dripped like the venom of a striking cobra, to shame.

‘Oh dear, those grags. Tell me now, which one was it? Come on, help me now.’

‘I can’t remember.’

‘And they did what? Surely not? Oh, it was your chum that we have in the van next door, was it?’

‘Well, it might have been, yes.’