He walked to his desk and straightened a pile of papers that was already straight, then crossed to the window again. He continued to speak with his back to me.

‘I had been involved in delicate negotiations for months with the French. There was a plan that our Queen might possibly marry one of the French princes, though the Catholic church in France was opposed to it and Her Majesty herself was uncertain . . . But whether or not that came to anything, we were trying to forge an Anglo-French alliance to resist the rising power of Spain, which was becoming a threat to all of us. Then that August the wedding was to take place between the French king’s sister (who was Catholic, of course) and Henry of Navarre, who was Protestant. Those of us who had been involved in drawing up the Treaty of Blois between England and France saw this as one more hopeful step on the road to reconciliation between the two countries and the two faiths.’

He sighed deeply and began to pace about the room. I had never seen Sir Francis, always so calm and contained, as agitated as this. I found I was biting my thumbnail and clasped my hands together to stop myself.

‘What we had not allowed for was the sheer evil malignancy of the Guises.’

‘That’s the Scottish queen’s French family, isn’t it?’ I felt I had been sitting silent for too long. Of course I knew it was. The Duke of Guise was behind most of the conspiracies Phelippes and I were tracking.

‘Yes. Because most of the leaders of the French Protestants, the Huguenots, were gathered in Paris for the wedding, the Guise faction saw this as an opportunity to massacre them. First there was a bungled attempt at assassinating Admiral Coligny, one of the prominent Huguenots. That was on the twenty-second of August. We didn’t know of it till later, but the Guises and their party then went to the king and swore there was a Huguenot conspiracy to kill him. He and his mother gave their blessing to the murder of every Protestant in the city.’

He came and sat down opposite me again, fixing me with a fierce look.

‘We were woken in the early hours of the twenty-fourth by the bells of Notre Dame ringing out. They were so close they seemed to be ringing inside our heads. It was a signal. And we could hear gunfire. Coligny was murdered in his lodgings, his body thrown out of the window and mutilated by the crowd below. Then the Catholics of Paris, led by the Guise faction, went on a blood-letting stampede throughout the city. I sent some of my servants out to discover what was happening. Two were slaughtered. The two who came back told us of what they had seen – bodies piled up in the street, houses looted and burning, the gutters running with blood. On the bridges over the Seine, men, women and children were lined up and thrown into the river, then shot as they tried to swim to safety, like sportsmen shooting ducks.’

He grimaced as though he had bitten on something rotten.

‘My wife and little Frances, and all the women, were terrified. We all were. I had the doors and windows barred and sent to the king for protection. He had a small guard posted around the house, but I put little trust in them. Already desperate people were pounding on the door, begging for sanctuary. Not only English citizens but Dutch and German and French. Even a few Italians and Swiss. I took them all in. We lived like a town under siege for days. In the end I was forced to hand over the French Protestants, which has haunted me to this day. I am sure they did not live to see the next dawn.’

He passed a hand over his face, as if it could wipe away the memories.

‘As soon as it was safe, I sent my wife and child home, though two of the men guarding them were recognised as English and beaten. But I had to stay in that filthy city until the following spring, stepping over blood-stained cobbles, past houses still marked with painted white crosses, so the murderers would know they were the homes of Protestants.’

His eyes bored into me, as if he needed to make me understand the full horror of what he was relating.

‘I think the most terrible thing about the whole terrible business was the atmosphere amongst the people of Paris. They treated it like a carnival. They paraded the bodies through the streets, played football with severed heads, butchered their victims and offered the body parts for sale, like meat on a butcher’s slab.’

He shuddered.

’These were their neighbours, their fellow-citizens of Paris, people they had lived beside in peace and friendship for years. They rejoiced. They dressed up in festive clothes. They gave thanks to God. Can you imagine anything more barbaric? More lacking in Christian feeling? Did you know that the Pope commanded the performance of a special Te Deum in celebration? He had a commemorative medal struck, showing an angel – an angel, mark you – flourishing a sword. The inscription read “Huguenots slaughtered”. In the view of the papacy, it was the greatest triumph for the Catholic church since the extermination of the Cathars.’

He wiped his mouth with the back of his hand, then got up and poured us each a glass of wine. As he handed me mine, I saw that his hand was shaking.

For a while neither of us said anything.

‘I am sorry, Kit,’ he said at last. ‘I do not usually speak of it, for the bad memories will haunt my sleep now. Even though she was so small at the time, Frances still has nightmares. My wife has never been able to speak of it since. But I wanted you to understand what we are fighting against. You have endured the Inquisition. I have lived through that massacre. If we let down our guard, both could be repeated here. No one will ever know how many thousands were murdered in France, for the madness spread out from Paris like the plague, infecting the whole country. There was a scramble of frantic refugees coming to England, some in boats so overcrowded that they sank and never reached our shores.’

He set down his empty glass on the edge of the desk. I was still sipping mine, for I was not accustomed to such a strong wine, red as blood. I shivered, seeing before my eyes what he had described. And what I remembered.

‘I understand that we must fight,’ I said. ‘And that the work I do with Master Phelippes is an instrument in that fight. What I do not understand is how I could serve you as an informant. Surely such men must be trained and clever in what they do? How can I hope to play the part?’ Even as I said it, the words echoed in my ears. Who better than I at playing a part? Had I not been playing a part for the last four years? But now I would be playing a part on top of another part. Boxes within boxes within boxes. I trembled at the thought of how easily I might slip up and give myself away.

‘There is a Catholic family living not far from my house Barn Elms in Surrey,’ he said. ‘Outwardly respectable. They attend our English church as they should, they are not recusants. However, Catholic priests have been seen to visit them. Not the most dangerous of the priests, but priests smuggled into this country, none the less. We think they may be providing a conduit for letters which we have not yet intercepted. At this particular time it is essential that we should know exactly what letters are passing to and fro, because matters are coming to a head. This very summer I expect the culmination of years of work. I do not want to make an overt raid on the house, because the line of communication will simply be diverted elsewhere. I want to make sure there is such a route and then control it.’

I nodded. This fitted with what was already being done by Phelippes and Gifford, a system of passing letters, to the Scottish queen or other conspirators. But if this was another route, all our efforts might come to nothing.

‘How can I help?’ I still could not see how this affected me.

‘I have been told that the family is looking for a new tutor for their son and daughter, a tutor in mathematics and music, their previous tutor having taken up a position in a noble household. You are skilled in both, I understand. It would be possible to place you in the household without anything linking you to me.’