The wider brief of the show is to reveal Milan as the place where Leonardo developed his ideas as a philosopher-painter. It is a theme with two strands: first, the way he turned the minute observation of Nature into a way to discover its laws and then use them to display the metaphysical as well as the physical world; and second, how art and the artist who made it were a reflection of the prince who ruled over them — perfect paintings were the product of a perfect state.

This perfection had unlikely beginnings. Ludovico and Leonardo were both born in 1452 with little indication of what was to come: the former, as the fourth son of a powerful dynasty, had expectations of wealth but not of power, the latter was the illegitimate child of a notary and a peasant.

 Ludovico's rise was tangled and his hold on Milan initially tenuous. His need for Leonardo was for his practical as much as his artistic skills, a fact Leonardo recognised in a letter announcing himself to Il Moro as a designer of "instruments of war" who "in time of peace...can satisfy as well as any other in architecture and the design of buildings...and in conducting water from one place to another" — as an engineer in other words. He ended the letter by stating, immodestly, "I can execute sculpture in marble, bronze and clay; likewise in painting, one could compare me to anyone else, whoever he may be."

The painting that substantiated this grand claim was the Virgin of the Rocks (1493-95) from the Louvre; which for the first time can be seen alongside the National's later version (1491-1508). Leonardo poured into the design everything he had learnt about aerial perspective and light and shade because, as he said, "a true understanding of all the forms found in the works of Nature...is the way to understand the maker of so many wonderful things".