But Fitcher need not have worried. Sir Joseph guessed immediately that he was from Cornwall and proceeded to ask a couple of questions about Cornish flora – the first was about the ‘bladder-seed’ plant, and the second about the flower called the ‘coral necklace’ – and Fitcher was able to describe and identify both of them correctly.

This was enough to satisfy the Curator, who rose from his seat and began to pace the floor. Then suddenly he came to a stop and said he was looking for someone to go to China – a sailor with some horticultural experience. ‘Do you think you might be the man?’

Fitcher, ever stolid, scratched his head and mumbled: ‘It hangs on the pay and the purpose, sir. Can’t say nothing till I know a little more.’

‘All right then: listen …’

It was well known, said Sir Joseph, that the gardens at Kew possessed sizeable collections of plants from some of the remotest corners of the earth. But there was one region which was but poorly represented there, and this was China – a country singularly blessed in its botanical riches, being endowed not only with some of the most beautiful and medicinally useful plants in existence, but also with many that were of immense commercial value. Just one such, Camellia sinensis – the species of camellia from which tea was plucked – accounted for an enormous proportion of the world’s trade and one-tenth of England’s revenues.

The value of China’s plants had not been lost on Britain’s rivals and enemies across the Channel: the major physick gardens and herbariums of both Holland and France had also been endeavouring to assemble collections of Chinese flora – and for considerably longer than Britain – but they too had not had much success. The reasons for the lack of progress were not hard to fathom and the most important of them, without a doubt, was the peculiar obduracy of the Chinese people. Unlike the inhabitants of other botanically blessed countries, the Celestials seemed to have a keen appreciation of the value of their natural endowments. Their gardeners and horticulturists were among the most knowledgeable and skilful in the world, and they guarded their treasures with extraordinary vigilance: the toys and trinkets that satisfied natives elsewhere had no effect on them; even lavish bribes could not persuade them to yield their riches. Europeans had been trying for years to obtain viable specimens of the tea plant, offering rewards that would have sufficed to buy all the camels in Araby – but the quest remained still unrewarded.

A further difficulty was the fact that Europeans were not permitted into the country’s interior and were thus unable to wander about, helping themselves to whatever they chose, as they were accustomed to doing elsewhere: in China they were confined to two cities, Canton and Macau, where they were closely watched by the authorities.