I realised that my voice sounded pathetic. I tried to assume a firmer tone. ‘Besides, there is my work at the hospital. It has been seriously neglected these last weeks. I may lose my position. When all this is over . . .’ I gestured vaguely at the neat stacks of paper on the desks and shelves, ‘when all this is over, I still have my living to earn.’

‘You need not worry about that,’ Sir Francis said. ‘I have explained to the governors of St Bartholomew’s that you are engaged on important work for the state. You will not lose your position at the hospital.’

As I slumped defeatedly, I saw them exchange a glance.

‘Come, Kit,’ Sir Francis said, ‘I would like to speak to you in my chamber. We will leave Thomas to his work.’

I got up to follow him, dreading what this might mean. As I picked up my woollen cap, he waved his hand and smiled. ‘Leave that dreadful cap here. I cannot think where Thomas found it.’

When we reached his room, he seated me in a comfortable cushioned chair, poured me a glass of wine, and sent one of his maidservants for food.

‘Have you eaten anything today, Kit?’ he asked when the girl returned with a tray of cold meats and bread.

‘Um,’ I said vaguely. ‘No, I do not think I have. I was too apprehensive this morning.’

‘And now it is well into the afternoon. As a doctor, you know that is folly. Now put down that glass and eat something, or the wine will go to your head.’

Obediently I helped myself to some cold beef and a chunk of fresh white bread. This was the Walsingham I remembered from Barn Elms, not the London Walsingham. He said nothing more until he was satisfied that I had eaten well.

‘Now,’ he said, sitting back in his chair and briefly stroking his beard.

Now, I thought, I am to have a dressing down for speaking well of Anthony Babington.

‘We have been asking a great deal of you lately, Kit. I think Thomas forgets that you are only sixteen. You have worked side by side with him for months now, with your extraordinary aptitude for analysing and breaking codes. He has come to think of you as a grown man, not a boy.’

I looked down at my hands. I did not want to give myself away by meeting his eyes. Also, I felt stupidly close to tears. Probably, I reasoned, it was merely fatigue, but if I began to weep I feared it might somehow give away the secret of my sex. I was a sturdy youth of sixteen, I reminded myself, not some weeping maiden.

‘I have to confess that it was my idea to place you in the Fitzgerald household,’ he said. ‘Everything seemed to fall into place. Had they not needed a tutor in mathematics and music, I might not have thought of you. As it was, you did admirably well and enabled us to intercept another courier route. Because you succeeded so well at the Fitzgeralds’, Thomas decided that he wanted to train you up in more of our work. As a code-breaker you are admirable, but if you could take on more varied work, you would be even more valuable to us.’

He smiled. ‘Your adventure down amongst the ports in Sussex showed that you were intelligent and observant. It was thanks to you – despite your little accident in the fishing village – that we discovered that Ballard and Barnes were back in the country and were able to follow them. We have had them under observation ever since. Ballard’s activities in particular are of interest.’

‘I was careless. I nearly ruined everything.’

He ignored this. ‘As for your mad race with the young trooper . . . Well, as you will have noticed, Thomas is no horseman. He was so impressed, that was one of the reasons we chose you to take the letter to Curll. That and your eminent suitability to play the part of a young messenger boy.’

I had to break in on this. ‘But, Sir Francis, I am a doctor. It has been my ambition all my life to follow in my father’s footsteps. He is the man I admire most in the world.’ I did not care whether that might sound arrogant, seated as I was in the room of one of the most powerful men in England. In Europe even. ‘All I want to do with my life is to heal the sick, or when they cannot be healed, to ease their suffering if I can.’

My voice was shaking with the passion I rarely revealed for my calling, but I had to make him understand that I was not willing to be shaped into their tool when my own ambitions lay elsewhere.

‘Yet,’ he said quietly, ‘when you were offered the chance to become a scholar at Oxford and study at the medical school there, you turned it down.’

I was stunned into silence. Of course he would have known about that. Sir Francis Walsingham had eyes and ears everywhere, but he did not even need the facilities of his intelligence service in this case. He had close links with the governors of St Bartholomew’s. No doubt he and Sir Jonathan Langley dined in each others’ homes. The offer and my refusal of it had no doubt been a minor item over the second glass of wine.

‘Well?’ he said.

‘There were reasons I could not accept,’ I said. ‘Of course I would have been glad to go, but I have been well trained by my father. And there are . . . family reasons why I could not accept.’ I lowered my eyes again and clenched my hands together, for they were shaking. Was he on the brink of discovering my secret?

He sighed. ‘I will not press you for your reasons, Kit, and I respect your desire to follow a very worthwhile profession, but at the moment we are caught up, all of us, in great matters of state. The letter you have been asked to take to Chartley, and the letter I hope will be sent in answer to it, may well bring this whole affair to an end. So you see that it is vital that you play your part a little longer.’

I have had too much of playing parts! The words roared so loudly inside my head, I feared I had spoken them aloud, but Sir Francis seemed not to have heard them.

‘I want you to cast your mind back,’ he said, ‘to a conversation we had in this room some weeks past. I told you then about what I had witnessed in Paris fourteen years ago. I did not tell you all the details, but perhaps I should, to make you realise the danger this country will be in if we drop our guard against invasion from France or Spain.’

He passed his hand over his face and I saw that there were beads of sweat on his forehead. I do not believe it was the heat of the day, for he was seated in front of an open window and with the coming of evening a cool breeze was blowing up from the river. Either he was ill with fever or the memories he was evoking had brought this on.

‘There were women eviscerated while still alive. And pregnant women who had their unborn children ripped from their wombs and smashed on the cobbles. Boys and men castrated, their private parts stuffed into their mouths before they were strangled or beaten to death. Ancient men and women forced to kneel at the feet of those ruffians and lick their filthy boots, then whipped along the street while the crowd howled in delight.’

Memory burst open in my head then, like a boil swollen with pus. I could smell burning flesh. I felt the slash of the scourge on my back. And another crowd howling in delight.

‘Stop!’ I cried and clamped my hands over my ears.

‘You are right.’ His voice had dropped from a passionate cry to a whisper. ‘You are right. I should not inflict this on you. But we must not forget! If men forget the evil that can be done, then evil will be done. Again and again.’

‘I do not believe that Sir Anthony Babington is capable of such evil.’ My voice was trembling, but I had to speak what I believed to be the truth.

‘I agree,’ he said. ‘I too do not believe Babington capable of such evil. However, it is men like Babington who make clear the path for other men to outdo the Devil himself. That is their danger. Good men, acting according to their principles, and bringing down evil on all of us.’

I looked at him blankly. I was so tired I could hardly think. ‘But how . . .?’ And then there came into my mind the face of Robert Poley. ‘You mean, people like Babington are used by evil men?