‘Two thousand?’ said James. ‘What do you mean?’

‘M is the Roman numeral for a thousand. Two Ms – two thousand.’

‘But why would you have it tattooed on your hands?’

‘Oh, people get tattoos for many different reasons,’ said Charmian. ‘But it most commonly means you belong to a tribe, or gang. The custom goes right back to ancient Egyptian times.’

‘What sort of people get tattoos?’ James asked.

‘In England? Well, they were first brought here in the eighteenth century by men who’d sailed to the South Seas with Captain Cook. They copied the idea from the natives out there. They started quite a craze. Did you know that King George has a tattoo?’

‘Really?’ said James, who couldn’t quite picture it.

‘Yes,’ said Charmian. ‘He and his brother both have dragons on their arms. It’s all down to their father, the old king. He had the Jerusalem Cross tattooed on to his arm in the Holy Land when he was Prince of Wales. Well, after that, everyone in smart society had to have a tattoo. You weren’t anybody unless you had one. King Edward had several more done and then got his sons tattooed in Japan by the celebrated master Hori Chiyo. But it all ended in 1891.’

‘Why? What happened?’ said James.

‘A man named Samuel O’Riley went and invented a mechanical tattooing device and suddenly everybody could afford one. Overnight tattoos changed from being the decoration of an aristocrat to the mark of a low life. But in many other cultures around the world they still use tattooing and ritual body-scarring as a sign of manhood.’

‘What would it mean if you had a scar from the corners of your mouth to your ears?’ said James, indicating the lines on his own face. ‘Would that be a ritual thing, too?’

‘No,’ said Charmian. ‘That would mean you were an informer. A criminal who’d given information to the police and been found out by his gang. It’s an underworld punishment. Rather gruesome. You swipe a long knife crossways into a man’s mouth and slice through both his cheeks.’

She demonstrated, with a sweep of her hand and a ghoulish look on her face. ‘He’s marked for life, you understand?’ she said. ‘It’s clear for all to see that he had betrayed his own kind. Criminals are a charming bunch. Talking of criminals, there was another article in The Times this morning about your friend Mark Goodenough’s family.’

‘Any news?’ James asked.

‘It didn’t say much more than what you’d already told me. They’re almost certain it was pirates. They’ve found the bodies of all the men, but still not the girl and her tutor. The fear is that they might have been taken for the white slave trade.’

‘I didn’t think there were still pirates in the world,’ said James. ‘When I think of pirates I think of the Spanish Main, Captain Kidd, Blackbeard and Long John Silver…’

‘Oh, as long as men have taken to the sea in boats there have been pirates,’ said Charmian. ‘And there always will be. We have a romantic notion of them, James, but in reality they are simple criminals, no different from any other burglar or thief, except that they’re usually more ruthless and murderous. You will just have to hope, James, that you never come face to face with one outside of a picture book…’