He took a key from a cabinet by his desk and walked over to the wall. His hands touched a mark on the plaster that was apparently no different from a dozen other marks, but this one caused a section of wall to swing aside on well-oiled hinges.

No-one knew all the passages and tunnels hidden in the walls of the Palace; it was said that some of them went a lot further than that. And there were any amount of old cellars under the city. A man with a pick-axe and a sense of direction could go where he liked just by knocking down forgotten walls.

He walked down several narrow flights of steps and along a passage to a door, which he unlocked. It swung back on well-oiled hinges.

It was not, exactly, a dungeon; the room on the other side was quite airy and well lit by several large but high windows. It had a smell of wood shavings and glue.

'Look out!'

The Patrician ducked.

Something batlike clicked and whirred over his head, circled erratically in the middle of the room, and then flew apart into a dozen jerking pieces.

'Oh dear,' said a mild voice. 'Back to the drawing tablet. Good afternoon, your lordship.'

'Good afternoon, Leonard,' said the Patrician. 'What was that?'

'I call it a flapping-wing-flying-device,' said Leonard da Quirm, getting down off his launching stepladder. 'It works by gutta-percha strips twisted tightly together. But not very well, I'm afraid.'

Leonard of Quirm was not, in fact, all that old. He was one of those people who started looking venerable around the age of thirty, and would probably still look about the same at the age of ninety. He wasn't exactly bald, either. His head had just grown up through his hair, rising like a mighty rock dome through heavy forest.

Inspirations sleet through the universe continuously. Their destination, as if they cared, is the right mind in the place at the right time. They hit the right neuron, there's a chain reaction, and a little while later someone is blinking foolishly in the TV lights and wondering how the hell he came up with the idea of pre-sliced bread in the first place.

Leonard of Quirm knew about inspirations. One of his earliest inventions was an earthed metal nightcap, worn ini the hope that the damn things would stop leaving their white-hot trails across his tortured imagination. It seldom worked. He knew the shame of waking up to find the sheets covered with nocturnal sketches of unfamiliar siege engines and novel designs for apple-peeling machines.

The da Quirms had been quite rich and young Leonard had been to a great many schools, where he had absorbed a ragbag of information despite his habit of staring out of the window and sketching the flight of birds. Leonard was one of those unfortunate individuals whose fate it was to be fascinated by the world, the taste, shape and movement of it . . .

He fascinated Lord Vetinari as well, which is why he was still alive. Some things are so perfect of their type that they are hard to destroy. One of a kind is always special.

He was a model prisoner. Give him enough wood, wire, paint and above all give him paper and pencils, and he stayed put.

ly Lord Vetinari said: 'Very well. I believe you're getting married at noon tomorrow.' His long fingers picked up the gilt-embossed invitation from the desk 'Yes. You can keep your badge, then. And have an honourable retirement. But I'm keeping the sword. And the Day Watch will be sent down to the Yard shortly to disarm your men. I'm standing the Night Watch down, Captain Vimes. In due course I might appoint another man in charge – at my leisure. Until then, you and your men can consider yourselves on leave.'

'The Day Watch? A bunch of—'

'I'm sorry?'

'Yes, sir.'

'One infraction, however, and the badge is mine. Remember.'

Cuddy opened his eyes.

'You're alive?' said Detritus.

The dwarf gingerly removed his helmet. There was a gouge in the rim, and his head ached.

'It looks like a mild skin abrasion,' said Detritus.

'A what? Ooooh.' Cuddy grimaced. 'What about you, anyway?' he said. There was something odd about the troll. It hadn't quite dawned on him what it was, but there was definitely something unfamiliar, quite apart from all the holes.

'I suppose the armour was some help,' said Detritus. He pulled at the straps of his breastplate. Five discs of slid out at around belt level. 'If it hadn't slowed down I'd be seriously abraded.'

'What's up with you? Why are you talking like that?'

'Lake what, pray?'

'What happened to the “me big troll” talk? No offence meant.'