‘I see,’ said Samuel, sitting down. He cut a piece of veal pie off a twenty-one pound slab, and pushed it into his mouth. ‘I suppose your poor mama left you quite a bit of disposable jewellery?’

‘I haven’t been through it all yet,’ Peter told him. ‘But I was mainly concerned about this,’ and he produced from his pocket the small drawstring purse, which he loosened, and then turned upside-down over Samuel’s workbench.

The diamond rolled out on to the bench, and lay on its side, sparkling in the gaslight. Samuel, his mouth still stuffed with pie, stared at it as if God had just dropped a third tablet of commandments from the heavens above.

‘What on earth …?’ he asked. ‘You’re not telling me that’s a real stone?’

Peter nodded. ‘I’m pretty well convinced of it.’

‘But that’s a diamond,’ said Samuel. ‘You don’t find diamonds in that sort of size. That’s as big as the Regent. Bigger. It can’t be real. Where on earth did you get it?’

‘My mother’s jewellery box.’

‘Not even in a safe? It can’t be real. My dear chap, if that were a real diamond, it would be worth … a million pounds. Maybe more. You wouldn’t keep it in a jewellery box. You’d have it locked up, in Coutts.’

‘Maybe you would, and maybe you wouldn’t. What burglar would ever suspect that a vicar’s wife would have a million-pound diamond in her jewellery box? A couple of rings, maybe; a pinchbeck pendant. But not a million-pound diamond.’

Samuel picked the diamond up and frowned at it. Then he reached for his jeweller’s loupe, his 10 × magnifying lens, and peered at it even more closely.

‘It’s difficult to tell in gaslight,’ he said. ‘But if it is a real diamond, it’s magnificent. A slight pinkish tinge to it, don’t you see? Very slight, but enough to make it a “fancy” diamond, and increase its value four to five times over, if you can find anyone to pay that sort of money.’

‘Then you think it’s genuine?’

‘My dear chap, I couldn’t tell you for certain. This is the whole illusion of the diamond business. Not even quite reputable dealers are capable of telling whether some diamonds are real diamonds or not. There are plenty of very capable fakes around these days: and if they’re mounted, they’re even harder to detect. Some tricksters set inferior diamonds in a fine gold or silver setting, you see, and paint the back of the gems so that they reflect more light. There was the famous rainbow necklace of the Romanoffs, for instance. George Kunz, an American gemologist, and a very sceptical fellow, discovered by scratching the backs of the diamonds with his finger-nail that they were nothing but second-rate stones with paint on them.’

‘But this stone isn’t mounted,’ said Peter.