In Flanders he bought vines, and watched them pruned of their yellow leaves and thick black grapes in preparation for their journey. He ordered their roots to be wrapped in damp sacking and plunged into old wine casks for their voyage home. He sent a message ahead of them, in the careful script which Elizabeth had taught him, so that a gardener from Hatfield would meet them with a cart on the dockside, to take them back and heel them in the same day, without fail, making sure to water them religiously at dawn every day until Tradescant came home.

The Prince of Orange’s gardener admitted Tradescant to the beautiful garden behind the palace of The Hague and showed him around. It was a garden in the grand European style, with large stone colonnades and broad sweeping walks. Tradescant spoke to him of his work at Theobalds, planting between the box hedges and replacing the coloured stones of the knot garden with lavender. The gardener nodded with enthusiasm and showed Tradescant his version of the changing style in a little garden at the side of the palace where he had used tidily pruned lavender for the hedges themselves. They made a softer pattern and had more variation of colour than the usual box hedge. They did not harbour insects and when a woman passed by, her skirts brushed against the leaves and released a cloud of perfume. When he left, Tradescant had a trayful of rooted cuttings and a letter of introduction to the great physic garden at Leiden.

He travelled overland to Rotterdam, uncomfortable on a big broad-backed horse, all the way seeking out English-speaking farmers who could tell him about the growing of their precious tulips. In the darkened cellars of ale houses, drinking a rich sweet beer which was new to John, called ‘thick beer’, they swore that the new colours entered into the heart of the flowers by slicing into the very heart of the bulb.

‘Does it not weaken them?’ John asked.

The men shook their heads. ‘It helps them to split,’ one of them volunteered. He leaned forward and breathed a blast of raw onion into John’s face. ‘To spawn. And then what do you have?’

John shook his head.

‘Two, where you had one before! If they are of another colour, and the colour often enters at the split, then you have made a fortune a thousand times over. But if they are the same colour but have doubled, then you have doubled your fortune at the least.’

John nodded. ‘It is like a miracle,’ he said. ‘You cannot help but double your fortune every year.’