Sometime in the late 1980s, Chinese jade and ceramics enthusiast Tony Miller was visiting the Chinese section of London's British Museum when he had something of an epiphany.

"Maybe it was a trick of the light," he says, "but I turned round and there he was staring at me. It took a while to register that he wasn't actually staring at me but through me, and the hairs on the forearm went straight up."

What had crept up on the Hong Kong career civil servant was a life-size and stunningly lifelike ceramic luohan or Buddhist saint, in the green, yellow and cream glazes known as sancai, typical of AD618-907 Tang dynasty tomb figurines, but here on a much larger scale.

This was a figure that, save for the addition of the elongated ears typical of Buddhist iconography, was far from the standardised serenity of most other luohan statues, and apparently a portrait from life. When Miller later stumbled across two similarly charismatic figures from the same set in New York's Metropolitan Museum, he began to wonder just how many there were around the world, and where they had come from.