‘May I?’ Without waiting for permission he sat down in my father’s carved chair while, at a gesture from him, we sank down side by side on one of the benches. I saw that I had crushed the fig to a broken pulp of seeds and golden flesh, and scraped my hand free of the mess on the edge of the table.

‘Not oysters for breakfast, then, Christoval, I see!’ He grinned knowingly and turned to my father. ‘Did your son tell you how he saved my life from a most virulent attack of food poisoning? Indeed I believe I may say that without his ministrations I might not be alive today.’

He turned to me. ‘You are surprised to see me no longer confined in the Marshalsea.’ Smiling, he tapped his nose. ‘Policy. Policy.’

I thought he smiled too much.

He stretched out his legs until his foot met and briefly fondled mine under the table. Hastily I tucked my legs back under the bench.

‘Now,’ he said, his manner quite changed. ‘To business. I have been making enquiries about young Christoval here. I learn that he is more than he seems.’

I swallowed painfully. It was as though the chill of hemlock began to seize my limbs. My father stiffened beside me.

‘Yes, I learn that young Christoval is a student of the mathematician and astronomer Thomas Harriot. He whom they call the “conjuror”.’

I opened my mouth to protest against this slur on my teacher, but he raised his hand to silence me.

‘I have spoken to Harriot,’ Poley continued, ‘and he tells me that Christoval is a gifted mathematician. Exceptionally gifted.’ He seemed always to address my father, but he watched me from the corner of his eye, and I sensed his foot groping again for mine. My heart began to pound. What did he want, this man with his genial exterior and the suggestion of threat in his voice?

‘Dr Alvarez,’ his manner became suddenly confidential, flattering, ‘I am sent to bring this young man to Sir Francis Walsingham, who wishes to look him over, with a view to offering him employment. As a mathematician.’

l determined to put a stop to this bland assumption that we would fall in with whatever plot he was hatching, for it seemed to me that no good would come of any further dealings with Master Poley.

‘I am already employed,’ I said, trying to keep my voice steady. ‘I work as an assistant physician at St Bartholomew’s.’ My father touched my arm to silence me.

‘Indeed, indeed,’ Poley said. ‘And what we have in mind would hardly take you from your duties. I would not wish to rob the poor and indigent of so promising a physician.’

He smiled that complacent smile, so that I longed to kick him hard, but I was mindful of my father’s fingers pressing into my arm.

‘No, Sir Francis would only require your services from time to time, when there is much work to be done. It need not take you often from your care of the sick.’

‘Sir Francis requires my services as a mathematician?’ It made no sense. Sir Walter Raleigh, perhaps, or one of the directors of the Spice Trust, might find me of use, if navigational calculations were needed for some new voyage. But Sir Francis? I knew little of what Mr Secretary Walsingham did, apart from keeping an eye on the Spanish and gathering information on the Queen’s enemies.

‘Come!’ Poley pushed back his chair so violently that the legs squealed in protest on the flagged floor. ‘I will explain as we go.’

‘Father?’ I looked at him, appealing with my eyes for him to forbid me to go. But he had become cowed and submissive as he had grown older. All he desired was the quiet life of an insignificant doctor, with a few investments in the spice trade so that he might lay aside a little gold to keep us both when he was too old to practice any longer. Only in dire circumstances would he defy a man as powerful as Sir Francis Walsingham. He avoided my eyes and patted my hand encouragingly.

‘Go with the gentleman, Kit.’ His voice was gentle, almost placating. ‘I am sure Sir Francis means you no harm.’

At that moment I realised that Poley had not introduced himself to my father. Was it right that my father should urge me to go with this dubious stranger, young and unprotected as I was – a man, for all we knew, who might have nothing to do with Sir Francis Walsingham?

‘Father,’ I said, ‘this gentleman has not even told us his name.’

‘But you know who I am, Kit,’ he said, and even as he spoke I did not like it that he used my familiar name. ‘I am Master Robert Poley, at your service.’ He gave my father a mocking bow and, gripping my elbow painfully, he steered me out of the door. I could barely catch up my cloak with my free hand before he had me in the street and was hustling me east, through Newgate.

‘Where are we going?’ I asked, struggling to fasten my cloak as he hurried me along with thrusts at my back.

‘To Seething Lane,’ he said abruptly, all pretence at genial manners gone now.

Seething Lane ran parallel to Mark Lane, where Hector Nuñez lived, but nearer to the Tower. I wondered whether I might be able to run off and seek sanctuary at the Nuñez house. As if he read my mind, Poley spoke again.

‘You come warmly recommended by Dr Nuñez, too, as well as the conjuror Harriot. Dr Nuñez believes you will be able to give Sir Francis good service. Such a remarkable young man!’

He gave the last word a kind of ironic flourish, then said no more. He walked fast for a man whose normal movements were languid and affected, and I had to hurry to keep pace with him. His movements, like his manner, underwent these sudden changes which I found as disturbing as the inexplicable summons to Walsingham. I recalled what I had said of Poley to Sara. There was a hint of violence in his abrupt changes.

We had nearly reached Tower Ward when I suddenly stopped dead in the street and refused to go further.

‘What if I do not wish to work for Sir Francis?’ I said, a little out of breath with the pace he had been setting, my voice sounding high and childish.

A baker’s boy with a tray of bread balanced on his head collided with me as I stopped, and cursed me as he grabbed to save his bread from falling. I ignored him and stood my ground, the London crowds parting around us where we stood like a boulder in a river. Sailors hurried up from their ships by the Custom House towards the ale-houses of the City, women knocked their market baskets against our shins, and a furtive mongrel leapt suddenly between Poley and me, grabbed one of the fallen loaves, and darted away down Little East Cheap.

‘Not wish to work for Sir Francis?’ His smile was mocking. ‘Here’s a fine opportunity many a young man would envy! A young man employed by Sir Francis might rise in service to Queen and State, even become a great man himself. Why, Sir Francis has risen from no notable family to be the second greatest councillor to the Queen, after Lord Burghley. And Lord Burghley himself was simple William Cecil not so many years since.’

He gave a sigh of pure pleasure. ‘Under such a Queen as Gloriana, may her radiant face ever shine upon us, men of simple yeoman families may come to great riches and power. Why, I myself, humble Robert Poley, am not without influence, and have hopes of great things hereafter. Why should a young man like yourself not profit likewise?’

His voice was mesmerising and for a moment I was almost carried away by it. Then I said, incautiously, ‘The men you speak of are all Englishmen, Master Poley. I am not.’

He looked at me thoughtfully, his head a little on one side.

‘True, true.’

He seized me again by the elbow and dragged me on along Tower Street to Seething Lane.

‘But what is this work you speak of?’ I asked. ‘I cannot see how I can be of any use to Sir Francis Walsingham.’

‘Code-breaking,’ he said impatiently. ‘Harriot tells me you have a true talent for the breaking of ciphers and codes. He sets them as puzzles for you, and has never defeated you yet, while you have twice defeated him with codes of your own devising.’