Painting Mona Lisa. Jeanne Kalogridis

Giuliano looked up at the blade with surprise. Behind Baroncelli stood Francesco de’ Pazzi, his dagger at the ready. Leonardo had provided the sketch, rendering the scene with as much accuracy as possible, although for the viewer’s sake, Giuliano was depicted as facing Baroncelli. Verrochio had made the cast from Leonardo’s drawing.

      Two days after the murder, Leonardo had dispatched a letter to Lorenzo de’ Medici.

       My lord Lorenzo, I need to speak privately with you concerning a matter of the utmost importance.

      No reply was forthcoming: Lorenzo, overcome with grief, hid in the Medici palazzo, which had become a fortress surrounded by scores of armed men. He received no visitors; letters requesting his opinion or his favour piled up unanswered.

      After a week without a reply, Leonardo borrowed a gold florin and went to the door of the Medici stronghold. He bribed one of the guards there to deliver a second letter straightaway, while he stood waiting in the loggia watching the hard rain pound the cobblestone streets.

       My lord Lorenzo, I come neither seeking favour nor speaking of business. I have critical information concerning the death of your brother, for your ears alone.

      Several minutes later he was admitted after being thoroughly checked for weapons – ridiculous, since he had never owned one nor had any idea of how to wield one.

      Pale and lifeless in an unadorned black tunic, Lorenzo, his neck still bandaged, received Leonardo in his study, surrounded by artwork of astonishing beauty. He gazed up at Leonardo with eyes clouded by guilt and grief – yet could not hide his interest in hearing what the artist had to say.

      On the morning of the twenty-sixth of April, Leonardo had stood several rows from the altar in the cathedral of Santa Maria del Fiore. He’d had questions for Lorenzo about a joint commission he and his former teacher Andrea Verrochio had received to sculpt a bust of Giuliano, and hoped to catch il Magnifico after the service. Leonardo only attended Mass when he had business to conduct; he found the natural world far more awe-inspiring than a manmade cathedral. He was on very good terms with the Medici. Over the past few years, he had stayed for months at a time in Lorenzo’s house as one of the many artists in the family’s employ.

      To Leonardo’s surprise that morning in the Duomo, Giuliano had arrived, late, dishevelled, and escorted by Francesco de’ Pazzi and his employee.

      Leonardo found men and women equally beautiful, equally worthy of his love, but he lived an unrequited life by choice. An artist could not allow the storms of love to interrupt his work. He avoided women most of all, for the demands of a wife and children would make his studies – of art, of the world and its inhabitants – impossible. He did not want to become as his master Verrochio was – wasting his talent, taking on any work, whether it be the construction of masks for Carnivale, or the gilding of a lady’s slippers, to feed his hungry family. There was never any time to experiment, to observe, to improve his skills.

      Ser Antonio, Leonardo’s grandfather, had first explained this concept to him. Antonio had loved his grandson deeply, ignoring the fact that he was the illegitimate get of a servant girl. As Leonardo grew, only his grandfather noted the boy’s talent, and had given him a book of paper and charcoal. When Leonardo was seven years old, he had been sitting in the cool grass with a silverpoint stylus and a rough panel of wood, studying how the wind rippled through the leaves of an olive orchard. Ser Antonio – ever busy, straight-shouldered and sharp-eyed despite his eighty-eight years – had paused to stand beside him, and look with him at the glittering trees.

      Quite suddenly and unprompted, he said, Pay no attention to custom, my boy. I had half your talent – yes, I was good at drawing, and eager, like you, to understand how the natural world works – but I listened to my father. Before I came to the farm, I was apprenticed to him as a notary.

       That is what we are – a family of notaries. One sired me, and so I sired one myself – your father. What have we given the world? Contracts and bills of exchange, and signatures on documents which will turn to dust.

       I did not give up my dreams altogether; even as I learned about the profession, I drew in secret. I stared at birds and rivers, and wondered how they worked. But then I met your grandmother Lucia and fell in love. It was the worst thing ever to happen, for I abandoned art and science and married her. Then there were children, and no time to look at trees. Lucia found my scribblings and cast them into the fire.

       But God has given us you – you with your amazing mind and eyes and hands. You have a duty not to abandon them.

       Promise me you will not make my mistake; promise me you will never let your heart carry you away.

      Young Leonardo had promised.

      But when he became a protégé of the Medici and a member of their inner circle, he had been drawn, physically and emotionally, to Lorenzo’s younger brother. Giuliano was infinitely lovable. It was not simply the man’s striking appearance – Leonardo was himself far more attractive, often called ‘beautiful’ by his friends – but rather the pure goodness of his spirit.

      This fact Leonardo kept to himself. He did not wish to make Giuliano, a lover of women, uncomfortable; nor did he care to scandalize Lorenzo, his host and patron.

      When Giuliano had appeared in the Duomo, Leonardo – only two rows behind him – could not help but stare steadily at him. He noted Giuliano’s downcast demeanour, and was filled with neither sympathy nor attraction, but a welling of bitter jealousy.

      The previous evening, the artist had set out with the intention of speaking to Lorenzo about the commission.

      He had made his way onto the Via de’ Gori, past the church of San Lorenzo. The Palazzo Medici lay just ahead, to his left, and he stepped out into the street towards it.

      It was dusk. To the west lay the high, narrow tower of the Palazzo della Signoria, and the great curving cupola of the Duomo, distinct and dark against an impossible horizon of incandescent coral fading gradually to lavender, then grey. Given the hour, traffic was light, and Leonardo paused in the street, lost in the beauty of his surroundings. He watched as a carriage rolled towards him, and enjoyed the crisp silhouettes of the horses, their bodies impenetrably black, set against the backdrop of the brilliant sky, with the sun behind them so that all detail was swallowed … Sundown was his favourite hour, for the failing light infused forms and colours with a tenderness, a sense of gentle mystery that the noon sun burned away.

      He became lost in the play of shadow on the horses’ bodies, on the rippling of muscles beneath their flesh, the spirited toss of their heads – so much so that as they came rumbling down upon him, he had to collect himself and move swiftly out of their way. He found himself standing on the southern flank of the Palazzo Medici; his destination, less than a minute’s walk away, was the Via Larga.

      A short distance in front of him, the driver of the carriage jerked the horses to a stop and the door opened. Leonardo hung back, and watched as a young woman stepped out. The twilight turned the marked whiteness of her skin into dove grey, her eyes to nondescript darkness. The drabness of her gown and veil, the downward cast of her face, marked her as the servant of a wealthy family. There was purpose in her step and furtiveness in her posture as her gaze swept from side to side. She hurried to the palazzo’s side entrance and knocked insistently.

      A pause, and the door opened with a long, sustained creak. The servant moved back to the carriage and gestured urgently to someone inside.

      A second woman emerged from the carriage and moved gracefully, swiftly, towards the open doorway.

      Leonardo spoke her name aloud without intending to. She was a friend of the Medici, a frequent visitor to the palazzo; he had talked to her on several occasions. Even before he saw her clearly, he recognized her movements, the cant of her shoulders, the way her head swivelled on her neck as she turned to look up at him.

      He took a step closer, and was finally able to see her face.

      Her nose was long and straight, the tip down turned,