In the same week, I met, in the apothecary's shop, a man who had been alive for ninety-nine years. He told me that the plague was caused by the tiredness of the earth and that this was but the first stage in the ending of the world. I nevertheless persuaded him to buy a bottle of Pearce's preventative, it being his ardent wish not to die until he had reached the age of one hundred. Before paying for his bottle, however, he asked me what was in the mixture. I told him that it contained crushed rue, sage, and saffron with boiled buttercup-root, snake-root and salt and that these ingredients were infused with Malaga. He smiled and nodded and pronounced the medicine "clever" and left, and as he went out I saw the apothecary bow obsequiously to him.

"Who is that old man?" I asked.

"Do you not know?" said the apothecary. "Do you not recognise the fleshy nose and something in the set of the mouth?"

"No."

"Ah. Well, to me, there is a family likeness. He is the only surviving brother of William Harvey."

For reasons which I do not completely comprehend, I was so affected by this revelation that, instead of returning to Cheapside as I had intended, I walked to a nearby tavern, The Faithful Dray, and ordered myself a small flagon of wine.

I had not drunk any wine for such a great while that a very little of it rendered me categorically drunk and I sat in my corner, foolishly sipping, glad that I was not known in The Faithful Dray and so forced to enter into any conversation. I was about to order a second flagon (having now remembered that solitary drinking can be an oddly enjoyable pastime) when I heard someone say, very meekly and politely: "Good morning, Sir Robert."

I looked up. A man stood before me, so cadaverously thin that his face resembled a skeleton more nearly than the painted faces of the Flagellants. On top of this gaunt visage, he wore a blond wig, once fine but now matted and greasy and clogged with old powder. He had on his back a torn green coat and the hand he held out to me was encased in a green glove. I stared and blinked. And then the knowledge of who he was seeped into me. It was Finn.

If he had not had the courage to apologise to me for spying on me for the King, I would have got up and left him, without any regard for his sorrowful condition. But the first words he spoke were words of apology, and following on these came the story of what had happened to him. And both the apology and the tale were pitiful, the first being very stammering and clumsy and the second being full of suffering and humiliation.

You will remember that, while I was delirious with the measles, Celia left me and returned to the King, taking Finn and the finished portrait with her.

During this journey, Finn began to dream. He dreamed of the King's hand slapping him on the back and pressing a purse full of gold into his palm. He dreamed of all the commissions to come (ah, the beauty of that word "commission" for all the unknown artists and poets!) and all the imaginary arcadian landscapes in which he would place his famous sitters.

After the dreams came the arrival. The portrait of Celia was unloaded from the coach and Finn carried it himself down the length of the Stone Gallery, believing that on this occasion the doors to the King's apartments would be straight away opened to admit him. But they were not. He waited in the Stone Gallery for two days, his mind so enchanted by his imminent preferment that he left his spot only once to eat a little meal of bread and sausage and to relieve himself. He slept with his head on the stone.

On the third day, he was summoned. The King looked down at the portrait (behind which Finn was humbly kneeling). His Majesty ordered lamps to be brought near to it. Then he leaned down from his great height and scratched at the pigment with his nail. A flake of burnt umber came off and adhered to his finger. He examined it and called for a silk handkerchief in which to deposit the flake. The handkerchief was brought to him. He flapped it at the picture. "Gaudy," he said, "and shallow. The antithesis of Lady Merivel. Take it away."

Finn saw the folly of protesting. He saw that to argue with the King would avail him nothing and lose for him the little money he would be given for the portrait, if he remained silent. And yet he protested. He came out from behind the picture and began to describe the pains he had taken with the thing, his care with the background and the fondness Celia had shown both for him and for the portrait. The King turned his back on him and walked away towards his bedchamber. Finn shouted after him that he owed him at least the seven livres promised in the contract and that no man would trust a King of England who did not keep his word. The King stopped in his tracks and called for his guards. Finn was arrested and sent to the Tower.

He languished in the Tower for seven months. He was not charged, he was forgotten. Celia's intercession eventually secured his release. He was ordered never to come to Whitehall again or to any place where the Monarch resided. He made his way to Norfolk, believing that Violet Bathurst would help him, but he found the Bathurst household in dereliction. Old Bathurst had died and been put into his mausoleum and Violet – whether in sadness for the loss of him or for the loss of me one cannot say – courted a daily oblivion in the fine Alicantes her late husband had hoarded in his cellar. She gave Finn fourteen shillings and the stuffed head of a marten cat and sent him away. Going out from her house, he was bitten by one of Bathurst 's hounds desperate for the taste of blood.

And so he returned to London, where he expected to die. He earned a poor living painting scenery at the Dukes Playhouse, but his anger against the King and against a world that would not value him was so great that it gnawed at his body as well as at his mind. It was, literally, wasting him.

All of this he told me at The Faithful Dray. We got so drunk together, we fell unconscious onto the floor and when we woke it was dark and the landlord was throwing a bucket of water over us. We went out into the street and vomited into the gutter. Then I took Finn home with me to Cheapside, and Katharine and Frances Elizabeth looked up from their sewing and stared at his hollowed, suffering face. I invited him to sit down at the table and after a while some knuckle stew with barley was served to us. As Finn spooned his to his mouth, I noticed tears coursing down his cheeks. They dribbled into his bowl of stew, making it more salty and watery than it already was.

Finn slept on a cot in the small dark room where Frances Elizabeth wrote her letters. He liked its smell of ink and paper and sealing wax and, after his first night in it, he asked me if he might stay a month or two ("only until the spring comes, Sir Robert…") at the low rent he could afford as a scenery painter.

Frances Elizabeth agreed. Gradually, her house was filling up with people, but she did not seem to mind. From being a very anxious-seeming and complaining person, she had become calm and enduring, and I surmise that she had found her years of solitude very difficult to bear. She never talked to me about Katharine's madness or about the day she had taken her to Whittlesea, or what had driven her to abandon her daughter. She never said that she believed Katharine was cured. It was as if she did not wish to remember the past – the death of her husband on the very steps of the Patents Office, the desertion of Katharine by the stone mason, the coming of sleeplessness and lunacy – but to savour the present and plan for the future, when her grandson would come into the world and grow to manhood and responsibility and let the women rest.

After the coming of Finn, however, when she heard me addressed as "Sir Robert", she began to write a letter to the Ecclesiastical Courts requesting that her daughter be allowed to divorce the stone mason "who has disappeared into the very aire" so that she could marry the father of her child. I sat down by Frances Elizabeth and gently took the quill from her hand. I intended to inform her that I, too, had a wife to whom the King himself had married me, but then I found I could not say these things to Katharine's mother, so I informed her instead that I did not believe there was any "e" on the end of "air" and that her writing was not as elegant in these letters as it sometimes was and that churchmen "being very fond of show and outward appearance" would be influenced in their decision by the beauty of the hand. So she tore up the letter and started it again, but I did not stay to watch her.