Towards the end of his life, Leonardo was plagued by ill-health – a stroke left him paralysed down the right side of his body.
Despite this, his notebooks reveal that he was surprisingly active, though it is likely that his assistants carried out most of the physical work. However, his mood deteriorated and he is thought to have been dogged by a persistent and overwhelming sense of pessimism.
He became increasingly obsessed with his experiments and scientific projects. These interfered with his artistic commissions and he became even more notorious for not finishing anything. He completed so few works in his lifetime that a whole industry sprang up around the search for 'real Leonardos' with many pastiches and copies being paraded as originals.
In April 1519 Leonardo, now 67, drew up his will. He left most of his works to his adored pupil and companion, Francesco Melzi. He died later that year and was buried in Amboise.