Paulette pointed to the writing: ‘Is the meaning of these lines known, sir?’

Fitcher nodded and turned the card over. Written on the other side, in a faint but distinctive copperplate hand, was an English translation:

The petals on their green tinged stem shine like the purest gold.

A purple eye looks up from the centre, setting the bloom aglow,

It remedies the pain of ageing bones and quickens the memory and mind,

It puts to flight the death that festers in the lungs.

Inscribed under these lines were the words: Hsieh Ling-yun, Duke of Kang-lo.

The Duke of Kang-lo, said Fitcher, was apparently a real person, not some mythical hero. He had lived in the fifth century of the Christian era and was regarded as one of the greatest of Chinese naturalists; these lines of his were thought to mean that not only could this flower reverse the effects of ageing, it could also be used to battle one of humanity’s most dreaded enemies: that scourge of the lungs – consumption.

Many years after Cuninghame’s death his papers had come into Sir Joseph’s hands. He too had come to be convinced that the Golden Camellia might be one of the greatest of all botanical discoveries: the plant-hunter’s Grail. This, said Fitcher, was one of the reasons why he had decided to send a trained horticulturist to Canton, at public expense – William Kerr.

‘But Mr Kerr did not find the camellia?’

‘No – but he did find evidence of it.’

The last consignment of plants that Kerr had sent back to Kew was exceptionally large, and to make sure of its safe arrival he had hired a young Chinese gardener to escort it to London. This boy’s name was Ah Fey, and although only in his teens he was exceptionally clever and remarkably skilled – he had succeeded in transporting the collection almost intact. On arriving at Kew he had also handed Sir Joseph a small ‘painted garden’ – a set of several dozen botanical illustrations made by Cantonese artists. Amongst them Sir Joseph had found a picture of an unknown flower, a camellia that was remarkably like the bloom depicted in Cuninghame’s painting.

Now, pulling another folder off the shelf, Fitcher took out a picture and handed it to Paulette. ‘Here – have a look.’

The picture was painted not on paper but on another material, something thicker, stiffer and of a pristine and polished smoothness: it was a substance made from the pith of a reed, Fitcher explained, and was much favoured by Cantonese painters. The sheet was about the size of a foolscap page and at its centre was a startlingly vivid burst of colour. The vibrancy of the image was enhanced also by the manner in which the painting had been crafted, with many layers of paint being applied upon the pith so that the subject seemed to stand out in relief against the smooth surface – it was a perfectly formed double blossom, with its petals arranged in several concentric circles. At the heart of the bloom lay a closely packed whorl of stamens that seemed to be lit from beneath by a glowing circle of mauve; this tint spilled over into the base of the petals, with the colours changing gradually as they moved away from the centre. The outer part of the corolla was a brilliant sunburst of gold.