He said something to his companions in Cantonese. Then I followed him to a small office in the corner of the basement, a tiny glass box where we could see all those grey, white and bald heads bent over their Mahjong tiles, although the noise was not quite so deafening.

There was a portable gas stove in the corner of his office, suitable for a camping trip, and Keith heated water in an aluminium pan and spooned some leaves into a cracked brown teapot. He offered me a small cup but I shook my head.

He settled behind his desk with a cup of boiling tea.

I remained standing.

‘You have not come to arrest me,’ he said. ‘Because you would not have come alone. And yet you have not come to thank me because you will not sit and drink tea with me.’

‘Who was she?’ I said. ‘The woman you came for in the Hopewell Centre?’

‘Her name is Li Jin Jin,’ he said.

‘Li,’ I said. ‘The same family name as you.’

He shrugged.

‘The same family name as ninety-three million Chinese. Li is the second most common surname in China. Many people are called Li. We are two a penny.’

I saw the glint of relish in his eye at his use of the phrase. Two a penny.

‘So I’m meant to believe that it’s a coincidence that you have the same family name as the woman you came for?’

The woman you killed for, I thought.

‘No,’ he said. ‘Jin Jin is the daughter of my brother. She is nineteen years old. A student in Wanchai, an area on Hong Kong island. There are many bad people there,’ said the head of the Wo Shing Wo. ‘And she met a man who told her that he could help her find work in London. We say – heiyu. A snakehead. You are familiar with that expression?’

He still sounded like the man I had met on that first day, in thrall to a version of the English language that he had heard on the BBC World Service.

‘A snakehead is a Chinese people smuggler,’ I said.

He gazed out through the glass wall, as if anxious to return to his Mahjong. It seemed to be a game without end. The washing of those bone tiles by all four players. The thundering clack as the tiles were matched and discarded to the cries of Chinatown’s most senior citizens. And then again the washing of the tiles, face down, all of it done in a hurry.

‘The Chinese invented many things,’ he said. ‘Do you know what we call the Four Great Inventions of Ancient China?’

‘Gunpowder, paper, printing and the compass,’ I said.

He was impressed. ‘You know China, Detective.’

‘Not really. But I worked Chinatown. When I was very young. When I was so young that I wore a police uniform. I don’t know China. I only know Chinatown, Keith.’