"Most probable. Relate them, then."

And so I begin. I do not merely set out for the King my thesis upon the tangled pathways to madness and the great reluctance of the world to explore the reasons why each one is taken, but lay before him everything I have learnt about my own foolishness and everything I have done to cure myself of it. In short, I anatomise my heart. I reach inside myself and take hold of it and lay it before him. And all the while, he listens sometimes grave, sometimes smiling, as if – even though he "knows it all and understands it all" – the story that I tell him is new and full of extraordinary things that have never before been told to him, neither in the Clock Room nor in any other place in his Kingdom.

Presently, it grows dark and Chiffinch brings lighted lamps and positions them round us.

We eat grapes, spitting the pips into a silver spitoon.

And the King comes at last to the subject of Celia, intertwined with which is the subject of his new love, Mrs Stewart, for whom, he whispers to me, "I have a most maddening folly, Merivel, so that were I with her upon a certain parapet, and supposed to be showing her the planet Jupiter, I would turn my back upon the entire starry universe just to cup her breasts in my hands."

We burst out laughing and this laughter turns into the kind of giggling we used to indulge in on spring afternoons on the Whitehall croquet lawns. And so the whole question of Celia is accorded no seriousness at all, as if she were a toy we had once thrown about from one to the other and had long grown tired of.

"I do declare," says the King at last, "that your idea of an annulment may be very useful, for then I shall be able to compensate Celia for the loss of my person at Kew by giving her a new husband: a young, handsome one this time! What do you think? Will this console her? What about Lord Greville d'Arblay's son, who is a very beautiful boy?"

I reply that I cannot – knowing Celia the little that I do -make any guess about who or what may compensate her, but the King, suddenly serious, shakes his head and says quietly: "That is not so. For we both know that nothing in the world will make up for what she has lost."

"Yes, we know it," I reply, "but it is Uncomfortable Knowledge."

"Precisely. So where shall we consign it?"

"I do not know, Sir."

"Yes, you do."

"Where, then?"

"To oblivion, of course."

And so we change the subject, and the great matter of my wife, the King's mistress, seems to pass out of my life entirely, so that my memory of Celia's face and of her singing voice fades and floats away into silence. And I feel a profound peace coming upon me, a peace such I cannot remember since I was a child and sat in the quiet of Amos Treefeller's room while my mother stroked my hair and told me it was the colour of sand.

In this state of quiet and content, I decide that I will tell the King about my child. And I discover that the story of Margaret moves him very much and he, in turn, tells me what a great love he feels for the first of his bastard children, the Duke of Monmouth, and advises me not to neglect my child "but let her into your life, Merivel, and give generously of your self to her."

I nod and promise that I will and then, because I am thinking about Margaret, I turn my head and look out of the open window eastwards along the river. And this is what I see. I see a great patch of orange light in the sky. I turn back to the King. "Sir," I say, "look there! If I am not mistaken a great part of the city is burning."

No sooner had I said this than we heard voices in the chamber beyond us and then there was a knocking at the door. The King rose at once, his mood of kindness leaving him on the instant, so that his countenance appeared suddenly dark.

Men began to crowd into the chamber. One I recognised as the clerk from the Navy Office, with whom I had once learned about the patience of a marble cutter. And it was he who now related to the King how an easterly wind had sprung up within the hour and was now blowing the fire "along a great pathway half a mile in width."

Forgetting me entirely, the King went with this man and the others into his Drawing Room and I heard him command them to fetch out the Lord Mayor and give him orders that all the wooden houses in the path of the fire be demolished, "this being the only way we can employ to halt it and put it out." The men went away in great haste and I heard the King shout to Chiffinch to go tell his brother, the Duke of York, what was happening and to send for a groom to saddle a fast horse.

And then he went rushing out of the great doors to the Stone Gallery without any word to me or any backward look and I was left alone in his apartments and the only sounds were the chiming and pinging of two hundred clocks, each in their own time beginning to strike the hour.

I remained where I was for several minutes, with my thoughts in a most tangled condition. Then I saw all at once what I had to do: I had to reach Margaret. I went down into the courtyard and asked for my horse. While waiting for her to be brought to me, a gust of wind blew off my hat and sent it spinning away into a flower bed. I retrieved it and held it in my hand. Then I mounted Danseuse and rode out of the gates and turned eastwards in the direction of the moneylender's house, which, as far as I had been able to determine from my sighting of the flames, lay in the very heart of the fire.

The wind was indeed fierce and blew into my face and ruffled Danseuse's mane. As we got near to the City, I saw countless pieces of charred matter, lighter than air, being carried on the wind and falling softly like snow all around me. And then I could smell the burning and with every breath seemed to breathe the smell more deeply into me, so that it made me choke and gag and I spat on the cobblestones.

The streets, now, were very packed with people, some moving with me into the stench and the smoke, carrying ladders or hauling handcarts, some in their nightgowns, just standing about in the street and staring, others giving way to fear and calling on God and the King to put out the flames.

I turned northwards up St Anne's Alley. I gauged that westward of London Bridge everything along the river was burning, so that to get to the money-lender's house I would have to skirt right round the fire. But the smoke now began to creep down into the streets like a fog and having turned north, then east, then north again and then east again I found myself in a street I did not recognise and with all sense of direction gone from me.

"Where am I? What street is this?" I asked about me, but no one seemed to hear me or pay me any attention, so all I could do was to press on, turning north, then east, then north again, trying to judge from the smell of the fire whether I was moving round it or still towards it and searching every narrow street for some name or landmark that would tell me where I was.

I was about to make another northward turn when I heard straight ahead of me a great commotion of people and then I saw through the smoke that a single tongue of flame had swept down upon the roof of one of the houses causing a sudden mighty panic with people rushing from doorways into the street and looking up at the flame that was beginning to spread out along the eaves, then running back inside to try to save their children and their possessions before the fire came to them. For they had not expected it so soon. The great front of fire was still many streets away. But some burning thing -a sheet of music, a plumed hat, or I know not what – had come out of the sky and fallen on this one house, and all around me I imagined the fire travelling thus, carried on the wind, on pieces of silk, on love letters, on lace collars, swirling and leaping and floating down at random and immediately catching hold.