Hearing King Arthur at St John’s Smith Square – round the corner from the Houses of Parliament and overlooking what was once Conservative Central Office – is to be reminded, if nothing else, of its status as establishment propaganda. Purcell’s 1691 entertainment, a sequence of songs and masques for a play by John Dryden, is one of the glories of English music theatre. But it also aimed at shoring up the Stuart dynasty by aligning its achievements with those of Britain’s legendary past.

The Knights of the Round Table are equated with the members of the Order of the Garter. Britannia, rising “in Triumph o’er the Main”, watches over a united kingdom that is at once a Restoration pleasure palace and a burgeoning imperial power “that all the World outvyes”. The point was forcefully brought home at the end of Paul McCreesh’s semi-staging with the Gabrieli Consort and Players, when the singers, hitherto performing from memory, produced union-jack-bound scores and formed themselves into a rigid lineup for the final hymn to St George. What started out as a witty, erotic romp was suddenly and ironically transformed into formal oratorio.

McCreesh is one of today’s finest Purcell interpreters, and musically this was rather special, played with an admirable mixture of sensuousness and majesty, and sung with consistent finesse and elan by nine singers sharing the songs and choruses between them. The high points, of which there were many, included Anna Dennis’s exquisite account of Fairest Isle, and a deliciously suggestive scene in which Helen-Jane Howells’s Cupid thawed out Ashley Riches’s handsome Cold Genius. Sophie Junker and Marcus Farnsworth generated considerable chemistry as a couple gradually giving in to their desire for each other. Nicholas Mulroy was outstanding in How Blest Are Shepherds. Beautifully done, all of it.