Purcell’s semi-operas get only occasional outings. They need, but rarely get, lavish staging, not to mention an orchestra, and a full cast of actors for the principal roles and singers for the lesser ones.

But the festival turned adversity into triumph. When the advertised theatre company did a runner, not only were new actors quickly rounded up, but many of the arranged singers were dragooned into speaking roles. This they did, as to the manner born.

John Dryden’s libretto was not given intact, but enough remained to leave a strong impression of style and story, if not political allusions. Its artistic advisers were Richard Jackson and Andrew Pinnock, the former delivering the wittily updated prologue.

Among the singing-actors two relatively minor characters caught the eye, Jason Darnell’s creepy Grimbald, amusingly drawn, and Helen Neeves as Philidel, who also delivered the show’s only palpable hit, Fairest Isle, with a sure touch. The engaging Frost Scene benefited from Bethany Seymour’s Cupid and Matthew Brook’s Cold Genius, duetting strongly.

Elsewhere, two lascivious sirens draped all over Nik Miller’s quizzical King Arthur and a quartet of clumsy yokels provided hilarious cameos.

Not all the straight actors projected well. But the suggestively costumed choir, and an orchestra among whom theorbos and recorders made a particular mark, wrought miracles of stamina and precision over more than three hours. A triumph indeed, directed from the harpsichord by Peter Seymour.