Ferron said, ‘I cast a net for men of his sort, and have caught what looks like a promising fish. He came to our attention - I mean the Inquisition’s - because he intends to travel to Cordoba, to the monarchs’ court, where he hopes to present his case.’

‘A case to do what?’

Ferron smiled. ‘To sail the Ocean Sea. To go west, if he can.’

‘Then such a man exists,’ Grace breathed.

‘Oh, yes. He was born in Genoa, this man, the son of a clothier. He is now thirty-four years old. It seems he was educated in a school run by the clothiers’ guild. But his learning is poor,’ he said dismissively. ‘He was restless, as many of that Italian breed are. He ran off to sea; he served on ships from his youth. He has sailed to Chios in the Aegean, and as far as Iceland in the Ocean Sea; he has visited Ireland, England, Flanders, and sailed down the African coast. He became a competent navigator, mapmaker and ship’s master, it seems. He made his money from his petty bits of commerce, as men of his kind do.

‘But his fortunes changed, this poor Dove’s, when he made a good marriage. He wed into a noble Portuguese family called Perestrelo. And this is where the dream was born. For his father-in-law, who died before the Dove married his daughter, served as a captain during the colonisation of Madeira, led by Henry the Navigator. The Perestrelos were given some land on the island of Porto Santo, off Madeira. Here it was that our Dove settled with his wife, and he began to go through his dead father-in-law’s maps and accounts of his explorations. He learned first hand how a new land may be made to turn a profit for its discoverer, and the nation that sponsors him.

‘And his eyes were drawn west. Porto Santo, I am told, is a haven for those who sail out into the fringe of the Ocean Sea in their little ships, explorers hunting down the African coast, slavers seeking a supply base. And many of them bring back tales of marvellous lands which lie to the west, always just out of sight . . .’

Out of all these fragments, in the head of the clothier’s son, a most remarkable dream was born.

Ferron said, ‘Perhaps if you sail west and keep on sailing, it would be more than new lands, new Madeiras, that you would find. For if the world is round, then perhaps you could sail around it. Perhaps you would end up coming around the curve of the earth and arrive in the east...’

James was astounded. He was educated; he knew his geography, and the shape of the world. But this was a category of journey that had never occurred to him before. ‘Can it be possible?’