Fifteen years ago, the Lam family business picked up a consignment of aged tea from a defunct Hong Kong restaurant. Its value has since risen by a factor of 10,000, as the Lams have found themselves part of a boom that is both investment fad and cultural obsession.

"It's like magic," managing director Sam Lam says, as he prepared tea according to the Chinese ritual, pouring boiling water through rough leaves and then into tiny cups to drink and spoke of the profits to be made.

The brew is of pu'er, a dark tea fermented after drying and whose taste mellows with age. Its history is thought to date back between 1,000 and 2,000 years, with legends of growers in mountainous Yunnan province ferociously guarding their cultivation secrets.