It was a pretty idea and it would have been a delightful compliment to His Majesty, except Tradescant’s goldfish were as elusive as swallows in winter. Whatever he did to the watercourse they slipped away downstream and mingled with the others: silver fish on one level, rainbow trout at the next, and dappled carp on the fourth level, who ate them.

Tradescant had tried nets, but they got tangled up and drowned themselves, he had tried building little dams of stones, but the water became sluggish and did not pitter-patter from one level to another as it should. Worse, when the water was still or slow it turned green and murky, and he could not see the fish at all.

His next idea was to build a little fence of small pieces of windowglass through which the water could flow and the fish could not swim. It was a prodigally expensive solution – to use precious glass for such a fancy. Tradescant scowled and placed the small panes – each one carefully rounded at the corners so as not to cut the fish – in a line, with only a small gap for the water to flow between each. When he finished he stood up.

His feet ached with standing in the cold water, and his back was stiff with stooping. His fingers were numb with cold – it was still only March and there were frosts at night. He rubbed his hands briskly on the homespun of his breeches. His fingertips were blue. He could hardly see his work in the failing light but he could hear the musical splashing of the water flowing down to the next pool on the next terrace. As he watched a goldfish approached the fence of glass, nosed at it, and turned back and swam towards the centre of the pond.

‘Got you!’ Tradescant grunted. ‘Got you, you little bastard.’

He chuckled at himself and clapped his hat on his head, picked up his tools, and set off for his shed to clean and hang them before he went home for his dinner. Then he stopped, listening: a horse, galloping at high speed, up the long spectacular winding drive and at full pelt to the front door of the house.

The messenger saw Tradescant. ‘Is His Grace at home?’ he shouted.

John glanced towards the brightly lit windows of the house. ‘Yes,’ he said. ‘He should be dining soon.’

‘Take me to him!’ the man ordered. He flung himself from his horse and dropped the reins, as if the high-bred animal hardly mattered.

John, wrenching his mind from yellow flowers, snatched at the reins and called for a groom. When one came running he handed him the horse and led the messenger into the house.

‘Where’s the duke?’ he asked a serving man.

‘At his prayers, in his library.’ The man nodded towards the door.

John tapped on the door and went in.