In July 2000, a British skydiver jumped from ten thousand feet under a parachute Leonardo da Vinci had drawn in 1485. It worked. In 2002, a hang-glider Leonardo had sketched in 1505 flew cleanly over the South Downs of England. It worked. In 1968, Oxford engineers confirmed the human aortic valve closes by exactly the vortex motion Leonardo had drawn in 1513. They had not built him for five hundred years.

Leonardo da Vinci spent forty years filling notebooks with designs the world was not ready for. Each time the world finally built one, the design worked exactly as he had described it.

The parachute. Codex Atlanticus, 1485. A pyramidal tent of waxed linen, twelve braccia square at the base. Leonardo wrote that a man could throw himself from any great height without harm. Five hundred and fifteen years later, the British skydiver Adrian Nicholas built it from period materials and jumped from a hot-air balloon over South Africa. He descended at a steady two metres per second. He said it flew smoother than any modern parachute he had ever used.

The hang-glider. Codex on the Flight of Birds, 1505. A canvas wing on a frame of black poplar and bamboo, the pilot suspended below. In 2002, Sky Sport Engineering built it using only materials Leonardo would have had, and the British paragliding champion Judy Leden flew it. It was pitch-stable in flight.

The bridge across Constantinople's Golden Horn. 1502. Two hundred and forty metres in a single self-supporting span. The Sultan's engineers said it was impossible. The sketch was lost for four and a half centuries. In 2001, the Norwegian artist Vebjørn Sand built it from laminated timber as a footbridge in Ås, near Oslo. It is still standing.

The human aortic valve. Anatomy notebooks, around 1513. Leonardo took an ox heart, filled it with wax, modelled the valve in glass, and watched grass seeds swirl through it as the valve closed. He drew the mechanism. Anatomists ignored him for four and a half centuries. In 1968, the Oxford engineer Brian Bellhouse filmed the valve in motion using X-ray dye. The blood swirled exactly as Leonardo had drawn it.

Leonardo died in 1519 at a manor in Amboise. He never saw any of his predictions tested. He had drawn them, labelled them in his backwards mirror-script, and closed the notebooks. The world is still catching up.

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