The story of Keats's tragic death is well known, and dramatising it against its true outline, at once stark and full of beautiful and terrible detail, is a difficult task. Here is the Keats who gave up contact with Fanny Brawne because it was too painful, who in the end asked that his Shakespeare and other books of poetry be removed, who instructed grimly that his epitaph should be "Here lies one whose name was writ in water". Here is the Keats who was a trained surgeon, who had nursed his brother through the consumption that had killed him, who recognised the coming agony, tried to prevent it by suicide, and was lovingly, and religiously, frustrated by Joseph Severn. Here is the Keats who was horribly afraid of the dark, and considerately brave. He was a tough intelligence, and Burgess uses one of his most uncompromising statements as his own epigraph. "I would reject a petrarchal coronation – on account of my dying day, and because women have Cancers." The grim voice of the dying surgeon speaks in counterpoint to the classical, flowery poet.

Burgess's novel – like all his novels – is about body and soul. Belli's blasphemous sonnets about the Incarnation represent one embodiment of spirit in earthy language. Burgess's Keats's dialogue, with its deliberately tasteless and inconveniently frank wit, is another embodiment. The soul is perhaps only the breath, the word of mouth. The title of the novel, Abba Abba, represents the cry of the dying Christ on the cross to his unhearing Father. It also represents, as Belli tells Cardinal Fabiani, the octave of the rhyme scheme of a petrarchan sonnet. For Burgess's Belli this sonnet is a kind of Incarnation. He says:

"The sonnet form must have existed in potentia from the beginning, but it was made flesh such as Petrarch. Behind the thousands of sonnets in the world, in Tuscan, Roman, French, German, even English, shines the one ultimate perfect sonnet… The wordless sonnet that still rhymes, that says nothing, having no words, but yet speaks… the ultimate statement whose meaning is itself. What is this, your eminence, but the true image of God?"

"Heretical, yes, you were right when you said that. You talk of an abstraction, a ghost."

"I talk of an ultimate reality."

In an essay published in 1967, in a collection entitled The God I Want, Burgess typically conducted his argument as a dialogue between two speakers, in this case "Anthony" and "Burgess". "Anthony", the sceptical voice, interviews "Burgess" who confesses to believing in a God whom he compares to mathematics, to grammar, and to the score of a symphony. Not, he says, the composer. The score, the notation, the form itself of the symphony, the potential experience of coherence and beauty. Like, he might have added, the sonnet form. Elsewhere, he said that his God did exist, but was like a Beethoven symphony eternally playing itself to itself, unconcerned with human plights.

Burgess reincarnates Keats's death, and Belli's Roman life and work, in his own vigorous English. He adds a further puzzle, in the shape of another alter ego, an Englishman called J. J. Wilson, descended from a Joseph Joachim Guglielmi, who lives in Manchester, dies in New York, shadows Burgess-Wilson's own career, translates Belli and is murdered in New York, having written several of Burgess's own rude juvenile sonnets.

Keats wrote his own epitaph, which is on his gravestone in the Protestant Cemetery in Rome. On Burgess's grave is written ABBA ABBA. A. B. is of course also Anthony Burgess.

A. S. Byatt, August 2000

"Isaac," he said. "Marmaduke. Which of the two do you more seem to yourself to be?" He mused smiling among the ilex trees. The dome of San Pietro down there in the city was grape-hued in the citron twilight.

"I have never much cared for either name," said Lieutenant Elton of the Royal Engineers. "At school they called me Ikey Marmalade."

"We're both edibles then. Junkets, me."

"Junkets? Oh yes. Jun Kets."

"To be eaten by Fairy Mab."

Elton did not catch the reference. He took out his handkerchief, coughed harshly into it, then examined the sputum in the lemon dusk. Satisfied with what he saw, he wrapped it and stowed it in his pocket. He said:

"It's the mildness here that is good. The winter will be very mild, you will see. Extremes are bad. On St Helena a raging summer is ready to begin. Not good for the lungs, that climate. Not good for the liver. Not good for anything."

"You spoke with Bony at all?"

"He waved his arms and said something about earthquakes or it may have been earthworks. Or earthworms, for that matter. I could not understand his French very well. I saw him digging a lot. Il faut cultiver notre jardin, he shouted at me. That's from the atheist Voltaire."

"You don't admire Voltaire?"

"A damned atheist."

"Here comes his sister."

"Voltaire's?"

"No, no, no. God in heaven, here truly comes his sister. To us."

Pauline Bonaparte glided in the dimming light, a couple of servants behind her, taking her evening walk on the Pincio. Elegant, lovely, with a fine style of countenance of the lengthened sort, fine-nostrilled, fine-eyed, she peered with fine eyes at the taller and more handsome of the two young men, gliding closer to peer better. Elton stood stiffly as though on adjutant's parade, suffering the inspection. She smiled and nodded and glided on. His friend laughed, though nervously.

"Fairy Mab will have you."

"Ah no. Ah no she'll not. I'm no whoremaster."

"Faithful to the one at home?"

"Yes, you could say faithful."

John brooded. "I too. The animal ecstasy of the flesh denied to us. We're not winds to play on that Aeolian Harp."

"What Aeolian Harp?"

"Her as Venus Reclining. Canova's work, apt for the hallway of a whorehouse. To be played on by any wind that blows, gale, zephyr, postcenal eructation." He paused to take in shallow breaths while Elton looked puzzled. "Can they be disjointed, disjuncted, disjunketed?"

"What?" They turned, in Pauline's far wake, towards the Spanish Steps.

"Love and the animal ecstasy."

"It is ennobled," said Lieutenant Elton RE, "by love. It ceases to be animal and becomes divine."

"In what bad poet did you read that?"

"I read no poetry. I read only engineering manuals and the Holy Bible."

"And Marmaduke said unto Isaac: Get thee gone and build thee an earthworm, earthwork I would say. And lo it was done and earth did quake with the work thereof."

"I think you laugh at me much of the time."

"Kindly, though. You will admit kindly." They started going down the Steps. "And talking of kindly, would it not be a kindly act to accost the Divine Pauline and speak of her brother, saying he is well and digging hard?"

"He is not well. They say he will be dead this time next year." And then: "Accost. I will keep out of the way of her accosting."

"You will be no accostermonger."

"You laugh at me much of the time."

They had come all the way down the Steps, quieter now than in the daytime, and John led Elton to the Barcaccia, whose water music could, with the evening stilling of the piazza, be clearly heard. "This," John said, "tries to sing me to sleep."

"You really are a poetical sort of fellow. And you have really brought out a book?"

"Alas."

Elton chuckled uneasily. "Will we meet tomorrow?"

"Under the ilexes. I've been searching for a rhyme for ilex. We have a terrible language for rhymes, Isaac Marmaduke. It makes poetical engineering most difficult. Here the people shout in rhyme without reason. Put on your armour, duke, be calmer, duke, cried Marmaduke. We're always being betrayed into comedy. You see how difficult it all is. From the sublime to the ridiculous is but a step."