An hour later, my father and I were at Whitehall. I had put on the cleanest coat I could find. I had washed all trace of Rosie Pierpoint's rouge from my face. My hair lay concealed and tamed under my wig. I had polished my shoes with a little furniture oil. I was excited, eager and full of admiration for the attention my father appeared to be getting from the King. But then, as we walked down the Stone Gallery towards the Royal apartments, I felt myself suddenly hesitate, gasping for breath. The public wandered freely here and all the people we passed looked at ease. But, to me, it was as if the presence of the King had altered the air.

"Come on," said my father. "Thanks to your acrobatics, we're already late."

The doors to the Royal apartments were guarded, but were opened to my father's nod. He held, over his arm, a silk pouch containing two pairs of satin gloves. We entered a Drawing Room. A fire was roaring under a vast marble mantel. After the chill of the gallery, I would have moved towards it, except that by now I felt almost too weak to move at all and wondered whether I was going to inconvenience my father (who had had enough embarrassment for one day) by falling down in a faint.

Moments passed, as if in a distorted, dreamlike time. A servant came out of the King's bedchamber and asked us to go in. I felt us glide, like skaters, across thirty feet of Persian carpet, stumble through the great gilded doors and fall flat on our faces at the feet of a pair of the longest, most elegant legs I had ever seen.

I realised, after a moment, that we were not prostrate, but only kneeling. Somehow, we the skaters hadn't fallen. This in itself seemed to be a. miracle, because everything around me – the canopied bed, the candle sconces, even the brocaded walls themselves – appeared to be moving, coming in and out of focus, first clear, then dim.

Then a voice spoke: "Merivel. And who is this?"

These days, enmeshed as I am in the tangle of the story, the voice returns to me frequently: Merivel. And who is this? First my name. Then a denial of all knowledge of me. Merivel. And who is this? And the memory is so fitting. I am not now the Merivel I was that day. On that November afternoon, I was shown a roomful of clocks, chiming and ticking in disunion. I was offered a sweetmeat, but could not swallow it. I was asked questions, but could not answer them. A dog snuffled at my foot and the touch of its nose felt repellent, like the touch of a reptile.

After an interminable time (and I do not know to this day how that time was filled up) I was out in the gallery again with my father, who began to shout at me for being a dumbcluck and a fool.

I walked alone back to Ludgate and climbed wearily to my room. There, in my shabby loft, the enormity of what had happened became suddenly and terrifyingly visible to me, as if a nest of maggots had all at once broken out of the wall. I had been within a glove's length of obtaining power, and I had not taken it. It had been there for me, and now it had gone for ever.

I began, like a pig in pain, to howl.

4. It is not clear what started the fire in my father's workshop in the New Year of 1662. It was of course crammed with wooden boxes and shelves holding the flammable materials of his trade: felt, buckram, goatskin, fur, lace, feathers, ribbons and bales of satin, camlet and silk. A small blaze begun by an upturned oil lamp or candle would have had ample substance on which to feed.

All that is known is that the fire began in the late evening, engulfed the workroom and spread ravenously upwards to my parents' apartments, where, it seems, they were at supper. Their servant, Latimer, managed to open a small skylight onto the roof, to scramble up and endeavour to haul his elderly master and mistress to safety. My mother had a hold of Latimer's hand when she suddenly fell back, retching and choking on the smoke. My father tried to lift her up again towards Latimer, but she was unconscious in his arms.

"Fetch a rope!" my father screamed, perhaps, but his instructions were muffled by the dinner napkin he had tied round his nose and mouth and Latimer could not make out what he was saying. He stared helplessly in, while all the time the smoke became thicker and darker and to belch out in his face while he clung precariously to the leads of the roof. He told me, in the bitter chill of the following morning: "I watched them die, Mr Robert. I would have given all my life's wages to save them, but I could not."

The burial was well attended. Lady Newcastle, for whom my father had made moleskin eye patches, arrived in a black coach with her horses decked with black plumes. The King sent two Gentlemen of the Bedchamber. Amos Treefeller, now in his dotage, hired a sedan-chair to carry him to the graveside, where he began to blub. The January wind carried the prayers up and away into silence.

The following day, I was summoned back to Whitehall.

The death of my kindly parents, as well as slaking for the time being my thirst for women, set moving in my anatomist's brain an acute awareness of the speed at which the body can succumb to death. I am not squeamish. At Padua, short of cadavers in the summer months, Fabricius once conducted an anatomy lesson on the body of a pauper that had been floating in the river for three days. The German students, notorious for their interruptions and disorderly behaviour, now took to vomiting and swearing all round me. I stayed perfectly well and calm and took notes as Fabricius worked. However, after my mother and father perished, I looked at my own body, of which I had never been at all proud, with a new distaste, with a new antipathy and with a new fear. And it was this fear which, in the contradictory workings of the world, brought me to the honour about to be conferred on me. Fear of death, you see, had lessened, if not obliterated, my fear of power. So when summoned to Whitehall, I was no longer overcome by the scent of majesty and thus no longer idiotic and dumb. My poor father would have been very pleased, in fact, by the way in which I was able to conduct myself.

The King received me in his Drawing Room. He talked at length and most flatteringly about my father's skill. He repeated his theory that no man should get above himself, but know his own talents and his own degree. I nodded and bowed. Then he said: "Out of my affection and admiration for your late father I have summoned you, Merivel."

"Yes, Sire," I said. "Thank you."

"But I have a task for you, a task in which you must succeed, because my heart will suffer very much if you fail."

"Did you know, Your Majesty," I ventured, "that the human heart – the organ itself, that is – has no feeling?"

He looked at me with sorrow. "Ah, Merivel," he said, "where have you learned that?"

"I have seen it, Sir."

"Seen it? But what we see is but a fraction of what it is. You, as a physician, must no doubt have understood that. Look at my hand, for instance. Wearing a glove made by your late father. What we see is the excellent glove, a little rucked on my fourth finger by the large sapphire ring I am fond of wearing. Whereas, underneath the glove is the hand itself, capable of a thousand movements, en l'air like a dancer, supplicant like a beggar, fisted like a ruffian, in prayer like a bishop… but then again of what fantastic complexity is the arrangement of bones in the hand…"

He went on to describe, with some degree of accuracy, the skeletal structure of the human hand. By the time he had finished, I thought it prudent not to return to the subject of the heart, but to allow him to come at last to his reasons for calling me to the palace.

"One of my dogs appears to be dying," he said. "The veterinary surgeon has bled him repeatedly, shaved the hair off his back in order to cup him, has tried without success lesions, emetics and purges, but the little creature doesn't rally. If you can cure him, Merivel, I will offer you a place here as a Court Physician."