De Chirico, one of the many moderns inspired by Giotto’s articulate distortions, wrote that in Giotto, “architectural sense attains high metaphysical space”. In his polyptych altarpieces, the success of the spatial design triumphs over the rules of representation, creating an otherworldly intimacy. The five framed panels, divided by decorated pillars, work as window frames. The saints can look out, and we can look in. In the Badia Polyptych (1295-1300), St Peter is thoroughly human — he looks like Peter Ustinov after receiving bad news — but at the same time, thoroughly transformed by his sacred, timeless responsibilities.

The unities of the Baroncelli Polyptych, a late masterpiece created for the Basilica of Santa Croce in Florence, are especially powerful. Again, the spaces are compressed and the perspective distorted. The perspective is so foreshortened that the back of the picture rises up, stacking the priests and nobles against a golden field, and pushing the consort in the foreground towards the viewer. Mary and Jesus are gentle giants; in reality, the angels attending them would be midgets. Yet together these images attain the condition of music. It is impossible not to stand before them without hearing heavenly harmonies from the viols, harps and trumpets of the musicians.

Italy creates another fleeting unity, by reuniting the polyptych with its decorative triangular cusp, borrowed from the San Diego Museum of Art. Two angels float towards God’s visage, holding smoked glass over their eyes, like airborne astronomers looking into the sun. Physical reality may never change, but the greatest art always changes before our vision.