A drawing of a dramatic flood in which the atmosphere above a wooded hill has materialised in a gigantic explosion, with jets of water shooting out from the centre. Square blocks of stone topple and fall from the sky. Above is a dark cloud from which jets of rain curl down. There are some notes written close to the upper edge.

A cataclysmic storm was one of Leonardo's favourite subjects during the last decade of his life, in both his drawings and his writings. These were in principle studies towards his never-completed Treatise on Painting, but the obsessiveness with which he approached the subject reveals a deep-seated fascination with destruction. There exist several long passages in which he describes with relish a huge storm overwhelming a landscape, and the futile struggles of man and animal against the forces of nature:

'Let there be represented the summit of a rugged mountain with valleys surrounding its base, and on its sides let the surface of the soil be seen to slide, together with the small roots of the bushes, denuding great portions of the surrounding rocks ... and let the mountains as they are laid bare reveal the deep fissures made in them by ancient earthquakes ... And into the depth of some valley may have fallen the fragments of a mountain, forming a shore to the swollen waters of its river, which, having already burst its banks, will rush on in monstrous waves; and the greatest will strike upon and destroy the walls of the cities and farmhouses in the valley.

Trees and plants must be bent to the ground, almost as if they would follow the course of the gale, with their branches twisted out of their natural growth and their leaves tossed and turned about. Of the men who are there some must have fallen to the ground and be entangled in their garments, and hardly to be recognised for the dust, while those who remain standing may be behind some tree, with their arms around it that the wind may not tear them away; others with their hand over their eyes for the dust, bending to the ground with their clothes and hair streaming in the wind.'

Of Leonardo's many drawings of deluges made at this time, ten are uniform in size and style, but not in technique - most are in black chalk only, though all are as meticulously worked up as the present sheet, which is finished with the pen to give a remarkably formal, measured quality to the destruction. Huge cubic blocks of a mountain arch over to crash down at the centre, sending curling waves of debris shooting out like shock-waves to blast the landscape along the lower edge of the sheet. Yet the dual nature of these drawings - both visionary and theoretical - is confirmed by the dispassionate inscription hidden among the clouds at the top, which reads:

'Of rain. You will show the degrees of falling rain at various distances and of varying degrees of obscurity, and let the darkest part be closest to the middle of its thickness.'

It is most probable that the deluge drawings were executed during the last couple of years of Leonardo's life, when he was living in France at the court of Francis I (reg.1515-47). The verso of each is blank, and framing lines are still visible along some of the sheet edges, suggesting that they were intended as finished works of art. Many of Leonardo's late drawings, such as his 'ideal heads' have similarly high degrees of finish; it seems that they were produced purely for his own satisfaction and never left his studio.

Text adapted from Holbein to Hockney: Drawings from the Royal Collection