Jeanne Kalogridis - Painting Mona Lisa

And there would have been time for him to take a single step forwards. To reach for the penitent’s hand. To move between Giuliano and Baroncelli.

Instead, his passion had reduced him to a witless bystander, rendered helpless by the panicked, fleeing crowd. And it had cost Giuliano his life.

He bowed his head at the weight of the guilt, then raised it again and looked in il Magnifico ‘s sorrowful, eager eyes.

‘I am certain this man was disguised, my lord.’

Lorenzo was intrigued. ‘How can you possibly know that?’

‘His posture. Penitents indulge in self-flagellation, they wear hair shirts beneath their robes. Then slump, cringe, and move gingerly, because of the pain each time the shirt touches their skin. This man moved freely; his posture was straight and sure. But the muscles were tensed.

‘I believe, as well, that he was from the upper classes, given the dignity and gentility of his aspect.’

Lorenzo’s gaze was penetrating. ‘All this you have ascertained from a man’s movements, a man who was draped in a robe?’

Leonardo stared back unflinching. ‘I would not have come if I had not.’

‘Then you shall be my agent.’ Lorenzo’s eyes narrowed with hatred and determination. ‘You shall help me find this man.’

So, over the past year, Leonardo had been summoned several times to the prison in the Bargello, to carefully examine the lips and chins and postures of several unfortunate men. None of them had matched those of the penitent he had seen in the cathedral.

The night before Baroncelli’s execution, Lorenzo, had sent two guards to bring Leonardo to the palazzo on the Via Larga.

Lorenzo had changed little physically – save for the pale scar on his neck. If his unseen wound had similarly healed, this day had torn it open, rendered it fresh and raw.

Had Leonardo not been so stricken, he might have delighted in il Magnifico ‘s unique features, especially his prominent nose. The bridge rose briefly just beneath the eyebrows, then flattened and abruptly disappeared, as if God had taken his thumb and squashed it down. Yet it rose again, rebellious and astonishing in its length, and sloped precipitously to the left. Its shape rendered his voice harshly nasal

That evening, il Magnifico wore a woollen tunic of deep rich blue; white ermine edged the collar and cuffs. He was an unhappy victor this night, but he seemed more troubled than gloating. ‘Perhaps you have already deduced why I have called for you,’ he said.

‘Yes. I am to go to the piazza tomorrow to look for the third man.’ Leonardo hesitated; he, too, was troubled. ‘I need your assurance first.’

‘Ask and I will give it. I have Baroncelli now; I cannot rest until the third assassin is found.’

‘Baroncelli is to die, and rumour has it that he has been tortured mercilessly.’

Lorenzo interrupted swiftly. ‘And with good reason. He was my best hope to find the third assassin; but if he does know him, he will take the secret to Hell.’

The bitterness in il Magnifico ‘s tone gave Leonardo pause. ‘Ser Lorenzo, if I find this third assassin, I cannot in good conscience turn him over to be killed.’

Lorenzo recoiled as if he had been struck full in the face; his pitch rose with indignance. ‘You would let my brother’s murderer go free?’

‘No.’ Leonardo’s own voice trembled faintly. ‘I esteemed your brother more highly than any other.’

‘I know,’ Lorenzo replied softly, in a way that said he did know the full truth of the matter.

Gathering himself, Leonardo bowed his head, then lifted it again. ‘I want to see the man brought to justice – to be deprived of his freedom, condemned to work for the good of others, to be forced to spend the remainder of his life contemplating his crime.’

Lorenzo’s upper lip was invisible; his lower stretched so taut over his jutting lower teeth that the tips of them showed. ‘Such idealism is admirable.’ He paused. ‘I am a reasonable man – and like you, an honest one. If I agree that, should you find him, he will not be killed but instead imprisoned, will you go to the piazza to find him?’

‘I will,’ Leonardo promised. ‘And if I fail tomorrow, I will not stop searching until he is found.’

Lorenzo nodded, satisfied. He looked away, and stared at a Flemish painting of bewitching delicacy on his wall. ‘You should know that this man …’ He stopped himself, then started again. ‘This goes far deeper than the murder of my brother, Leonardo. They mean to destroy us.’

‘To destroy you and your family?’

Lorenzo faced him again. ‘You. Me. Botticelli. Verrochio. Perugino. Ghirlandaio. All that Florence represents.’ Leonardo opened his mouth to ask Who? Who means to do this?, but Lorenzo lifted a hand to silence him. ‘Go to the piazza tomorrow. Find the third man. I mean to question him personally.’

It was agreed that Lorenzo would pay Leonardo a token sum for a ‘commission’ – the sketch of Bernardo Baroncelli hanged, with the possibility that such a sketch might become a portrait. Thus Leonardo could honestly answer that he was in the Piazza della Signoria because Lorenzo de’ Medici wanted a drawing; he was a very bad liar, and prevarication did not suit him.

As he stood in the square on the cold December morning of Baroncelli’s death, staring intently at the face of each man who passed, he puzzled over il Magnifico’s words.

They mean to destroy us …

I will always remember the day my mother told me the story of Giuliano de’ Medici’s murder.

It was a December day more than thirteen and a half years after the event; I was twelve. For the first time in my life, I stood inside the great Duomo, my head thrown back as I marvelled at the magnificence of Brunelleschi’s cupola while my mother, her hands folded in prayer, whispered the gruesome tale to me.

Midweek after morning Mass, the cathedral was nearly deserted, save for a sobbing widow on her knees just beyond the entry, and a priest replacing the tapers on the altar’s candelabra. We had stopped directly in front of the high altar, where the events of the assassination had taken place. I loved tales of adventure, and tried to picture a young Lorenzo de’ Medici, his sword drawn, leaping into the choir and running past the priests to safety.

I turned to look at my mother, Lucrezia, and tugged at her embroidered brocade sleeve. ‘What happened after Lorenzo escaped?’ I hissed. ‘What became of Giuliano?’

My mother’s eyes had filled with tears. She was, as my father often said, easily moved. ‘He died of his terrible wounds,’ she said, and sighed. ‘And the executions of the conspirators were horribly brutal … It was a horrible time for Florence.’

Zalumma, who stood on her other side, leaned forward to scowl a warning at me.