I smiled. ‘Was it a recipe for gold? And somehow incomplete?’

My father smiled back. It was a family joke that we could live like Spanish grandees on the proceeds of the alchemist books that promised to deliver the recipe for the philosopher’s stone: the instructions to change base metal into gold, the elixir of eternal life. My father had dozens of books on the subject and when I was young I had begged him to show me them, so that we might create the stone and become rich. But he had showed me a dazzling collection of mysteries, pictures and poems and spells and prayers, and in the end, no man any the wiser or the richer. Many men, brilliant men, had bought book after book trying to translate the riddles that were traditionally used to hide the secret of alchemy, and none of them had ever come back to us to say that they had found the secret and now would live forever.

‘If any man ever finds it, and can make gold, it will be John Dee,’ my father said. ‘He is a most profound student and thinker.’

‘I know that,’ I said, thinking of the afternoons when I had sat on his high stool and read passage after passage of Greek or Latin while he translated as swiftly as I spoke, surrounded by the tools of his craft. ‘But do you think he can see into the future?’

‘Hannah, this man can see around corners! He has created a machine that can see over buildings or around them. He can predict the course of the stars, he can measure and predict the movements of the tides, he is creating a map of the country that a man can use to navigate the whole coastline.’

‘Yes, I have seen that,’ I concurred, thinking that I last saw it on the desk of the queen’s enemies. ‘He should have a care who uses his work.’

‘His work is pure study,’ my father said firmly. ‘He cannot be blamed for the use that men make of his inventions. This is a great man, the death of his patron means nothing. He will be remembered long after the duke and all of his family are forgotten.’

‘Not Lord Robert,’ I stipulated.

‘Even him,’ my father asserted. ‘I tell you, child, I have never met a man who could read and understand words, tables, mechanical diagrams, even codes, more quickly than this John Dee. Oh! And I nearly forgot. He has ordered some books to be delivered to Lord Robert in the Tower.’

‘Has he?’ I said, my attention suddenly sharpened. ‘Shall I take them to Lord Robert for him?’

‘As soon as they arrive,’ my father said gently. ‘And, Hannah, if you see Lord Robert . . .’

‘Yes?’

‘Querida, you must ask him to release you from your service to him and bid him farewell. He is a traitor sentenced to death. It is time that you said farewell.’