The man who discovered the corpse was called John Floyd. But he was known to everybody – sometimes even to his wife – as Tom Turdman. He was as brown as his name, and a finder of unwanted trifles, discarded memories and excreted secrets.

Jerusalem occupied eight or nine acres of ground. The college was surrounded on three sides by a high brick wall upon a mediaeval base of rubble and dressed stone, and on the fourth side by the principal buildings. The walls were topped with rows of spikes. Behind the chapel, the Long Pond stretched in a curve towards the south-east. It was fed by a stream that the friars had culverted under the walls long ago, before Jerusalem was even thought of. On the far side of the pond were the Fellows’ Garden and the Master’s Garden. Most of the town lay some way off on the other side of the irregular huddle of college buildings.

The only sounds were the clack of Tom’s overshoes, wooden pattens, and the trundling of the iron-rimmed wheels of his barrow on the flagged path. He visited four colleges: Sidney Sussex, Christ’s, Jerusalem and Emmanuel. He preferred to work in winter because he was paid by volume, not by the hour, and the smell obliged him to visit more frequently in the summer. He worked for a retired corn chandler whom the undergraduates called the merchant of shit. His employer derived a modest income from selling scholarly manure to farmers and gardeners.

This morning Tom was now so cold that he could hardly feel his hands. He had just emptied the Master’s privy, never a pleasant task, and wheeled his barrow along the flagged path at the back of the Master’s Lodge, which was unexpectedly productive. The path led to a gate, which the head porter, Mr Mepal, had just unlocked for him, and then over the Long Pond by way of an intricately constructed wooden bridge. The barrow wheels rumbled like muffled thunder on the wooden planks. He turned left towards the little boghouse the bedmakers used, which was modestly tucked away on the far side of the college gardens.