Gay plays crowd the theatrical canon. There are the necessary enigmas of Noël Coward, like The Vortex or Design For Living, which are slyly aimed at an audience of knowing code-breakers. There are the proud, defiant (and rather tedious) pleas for understanding like La Cage Aux Folles. And the gayest of them all, My Night With Reg, is also the least overtly gay because it dispenses with all homosexual caricatures. There isn’t an interior designer, a flight steward or a hair stylist in sight, let alone a Liberace fetishist, or a Maria Callas wonk.

The characters are mainstream yuppies who are exactly like hetero folk, except that they seduce one another with very little encouragement and an enviably high success rate. We’re in the 1980s. Aids, represented by the shadowy and unseen Reg, haunts the action. The characters are university chums who meet up ten years after graduation and slowly realise that most, and perhaps all, of the group have embraced a joyful tryst with Reg and his lethal body fluids.

Writer Kevin Elyot arranges an ingenious tapestry of affairs, crushes and unrequited ardours in a script that operates on several levels. It’s a flatshare comedy crammed with engaging figures of fun. Petty, nit-picking Bernie tolerates the affairs of his randy thuggish boyfriend because he’s terrified of getting the elbow. Cool, suave John is adored by Guy, the chubby loser, who can’t find the courage to declare his love. The flat he owns is being decorated by a fit young Brummie named Eric whom all the older men covet madly, but he barely notices as they drool and pant and ogle. Comedy aside, there’s a whole heap of suspense here. It’s like a country-house thriller. Anyone could croak at any time, and even the near-celibate Guy is at risk thanks to an unprotected summertime fling.

Robert Hastie’s production looks superb, and feels it too. Jonathan Broadbent’s Guy is a seething barrel of comic frustration who never comes across as contemptible or sad. Julian Ovenden plays John as a cerebral, slightly shifty hunk while Geoffrey Streatfeild is dashingly charismatic as Reg’s long-term boyfriend Daniel. It’s notable that Daniel’s flouncy manner is the play’s only camp gesture. Elyot was aiming for a universal audience, straight and gay alike, because Aids was not remotely homophobic. It killed indiscriminately.

When it first arrived in the 1980s it seemed likely, or even inevitable, that humanity would expire before a remedy could be found. I remember being told that in 1979 Aids had claimed 14 lives. Five years later the figure was 14,000. At that rate of acceleration, the disease would wipe out the earth’s entire population, twice over, by 1989. Even heterosexuals felt doomed. This dark background noise has faded from our collective memory, and younger audiences may need a tutorial in epidemiology in order to feel the full impact of the play. There’s one serious failing. It runs for 120 minutes uninterrupted. Why? Elyot sorts his script into two uneven chunks using the 5:3 ratio. This allows him to pace the evening according to the play’s emotional temper. The exuberant, quickfire first act lasts 75 minutes. The more muted and elegiac second act runs for roughly half of that. This is calibrated deliberately. The audience gets a chance to catch its breath at the break, to sample a shot of something sturdy, and to prepare for fresh weather in the second half. All that craftsmanship is lost. Along with a thousand quid in bar profits. The last production I saw that summarily ditched the interval was The Drowsy Chaperone in 2007. Got rave reviews. Closed within weeks.

No interval at Islands either. Just as well, really. Few sane ticket-holders would return given an escape route. It’s a pity. The show’s theme, inequality, deserves intelligent debate but this is a smug, weightless lark played by a posse of needy show-offs capering around a fairy-tale realm obscurely connected to a parallel society called ‘Shit World’. That charming name typifies the show’s aesthetic. The set is an explosion of scruffy bric-a-brac. The script toils through a desert of opaque speeches, humourless skits, jazz strum-a-longs, passages of artery-hardening dialogue and free-form verbal cacophonies masquerading as political thought.

The cast of chirruping thesps (all young enough to look effortlessly alluring) have achieved the astonishing feat of choosing Oxfam cast-offs and smeary facial décor that make them appear physically repulsive. I lost count after the first 23 spectators had walked out. Others would have followed but the seating arrangements prevented inconspicuous departures. At curtain-fall many viewers declined even to pretend to clap. I’ve never seen that before. I’ve never seen anything like this before. I expect the Bush programmed the debacle without knowing quite what its audiences would have to endure. Everyone involved needs their head examined.