Cooper reached out a hand to touch the nearest one. He ran his fingers over the rough stone, and felt the chisel marks made by the mason. Despite the occasional bits of damage, the sarcophagi were remarkably intact for their age. Whatever their age was, exactly. They seemed to belong to that murky period of history beyond the medieval.

‘Roman?’ he said. ‘They’d be about two thousand years old, I suppose.’

‘Oh, perhaps of that era,’ said the professor. ‘It’s impossible to date them with any accuracy. Their design never really changed. It was so simple and functional that there wasn’t much you could do to tinker with it.’

‘But they’re just stone coffins, aren’t they? Old churches often have them in their graveyards.’

Robertson shook his head. ‘Most people think of them as stone coffins. And I can understand how they might give that impression, at first glance.’

The sarcophagus nearest to Cooper was one of the bigger examples, its upper end at eye level against the church wall. It tapered towards the foot, and the mason had hacked a vaguely human shape out of the stone, including the outline of a head and shoulders.

‘There’s no mistaking that they’re designed to contain a body.’

‘Ah, but there are differences. For a start, these sarcophagi never possessed lids. They were always open to the air like this.’

For some reason, Cooper felt reluctant to examine the smallest sarcophagus, so he concentrated on the bigger ones instead.

‘Of course, the distinctive feature is the hole in the bottom. I wouldn’t expect that in my coffin.’

Robertson nodded encouragingly, as if to a student who was none too bright but was making an effort. ‘Exactly.’

Moving closer, Cooper tilted his head. The base had been shaped more carefully from the stone than at first appeared. Despite the crudeness of its construction, the surface showed a distinct dip towards the centre, where a hole a couple of inches across had been drilled through the stone.

‘The hole must be there for drainage. If these things didn’t possess lids, there had to be some way of letting the rain run out, or they’d be full of water.’

‘No, no,’ said Robertson. ‘Sarcophagi were kept under cover. They had to remain dry. It was essential to the process.’

‘But …?’

‘Well, you’re partly right, DC Cooper. However, rainwater wasn’t involved. Yes, sarcophagi were designed to provide drainage – but it was the drainage of body fluids.’

‘Ah.’