The giant – “il gigante” – in question is a huge block of marble from which will be hewn the statue now known as the Michelangelo David. Antony Sher’s gripping and ambitious new play shows how it nearly became known as the Da Vinci David.

The two artists were in Florence at the same time, around 1501, and there is a theory that the model for the sculpture was one of the quarrymen at Carrara, where the stone comes from (Henry Moore also quarried at Carrara and I myself have a neutral little slab of the stuff on my mantelpiece). So, in Sher’s invention, the artists first of all vie for the commission and then for the attention of the unspeakably beautiful young man, Vito, who happens to be married with a young child (we never see his family).

Old Vito (Richard Moore) introduces the story, giving it an epic, Brechtian dimension from the start, while the literally stunning newcomer Stephen Hagan – fresh from LAMDA, with a Belfast accent that indicates provincialism in Florence and an unstudied physical grace that totally belies his inexperience on stage, let alone the novelty of standing about with no clothes on – unwittingly inveigles himself into their affections.

There are several strands to Gregory Doran’s compelling production. John Light’s obsessive, dust-coated Michelangelo is a bearded solitary with a gruff exterior, while Roger Allam’s silky, seen-it-all Leonardo is a political operator as well as the visionary inventor with dreams of flying. What Leonardo calls “the accident of beauty” is the spur to their rivalry.

The marble sits on the stage until the great moment when it is winched into position in the workshop rotunda. William Dudley’s design is a scaffolded studio that can double as a setting for Leonardo’s Florentine masque about Ganymede, transported by the eagle of Zeus, and of course played by a soaring Vito in a huge pair of wings. Just as we see an astonishing replica of the statue stepping out of the stone, so the play is constructed by Sher, in a fashion both imaginative and workmanlike, from these ideas of art, beauty, flight and spirituality.

And the Florentine politics – in which sodomy is all the rage – lend a gritty, comic context, with a pair of religious bad boys causing trouble, a wonderfully devious and sly Machiavelli (Stephen Noonan) manipulating the contest and the richly robed doge (Philip Voss) leading the official appreciation of art society.

One or two scenes in the second act lose the plot, and the play is 15 minutes too long. Otherwise, this co-production by Hampstead and Thelma Holt of a play first commissioned by the Royal Shakespeare Company is a credit to all concerned.

- Michael Coveney