The Exorcist opened in 1973 accompanied by much hoo-ha in the press. Scenes of panic, nausea and fainting were recorded at every performance. Movie-goers showed up to witness mass hysteria rather than to enjoy a scary movie. This revival, produced by Bill Kenwright, targets the early 1970s demographic. At press night, the stalls were thronged with pensioners eager to relive a lurid evening from their adolescence. As one who dislikes shocks of any kind, I sat through this ordeal with my eyes bent towards the floor and my fingers wedged so firmly in my ears that their tips turned crimson.

The show opened with a CRUMP loud enough to shake the theatre to its foundations. Everybody screamed. Then they all giggled. This pattern of shrieking followed by feathery tittering continued throughout. At times the bangs and flashes were so punishingly invasive that I felt as if my head were exploding. Crash-landing on a rush-hour motorway must feel like this, only quieter.

The story follows Satan’s plan to possess a 12-year-old girl and to use her as bait to capture a higher prize, the stainless soul of a Catholic clergyman sent to chase out her demonic captor. This strategy is based on rather dated moral assumptions. Gone are the days when Catholic priests were considered saintlier than the general populace. The show is furnished with all the crass apparatus of the horror genre. Creepy lighting, shadowy attics, eerie glimpses down darkened corridors, frosted windows across which horrid silhouettes may lurch at any moment. Everything is arranged to keep one in constant fear of some ghastly eruption of light and noise. The voice of Satan, uncredited in the programme, sounds like Ian McKellen doing a camp pastiche of silky criminality.

At one point I raised my eyes from the floor to see the possessed girl in blood-soaked pyjamas cavorting on a mattress with a silver crucifix. My next upward peep disclosed the girl squirting her fellow actors with yellow vomit. This regurgitation is, famously, the show’s artistic highlight, and it made me wonder about the contract between the entertainer and the entertained. If the purpose of a scary play is to send punters running for the exits, it follows that the finest horror production is one that no viewer has watched to its conclusion. And though the crowd remained in their seats throughout, I feel obliged to hail this two-hour torture session as a triumph. Rarely has the West End seen such a thoroughly draining and nasty experience. Punters will go home transformed into sweaty, nightmare-haunted insomniacs. Enjoy.

The contrast could hardly be greater with Slaves of Solitude. This adaption of Patrick Hamilton’s wartime novel is about quietness, repressed sexuality and the tattling of malicious tongues behind twitching net curtains. The scene is a genteel boarding house in Henley, 1943. With the men away at war, the town is populated by spinsters, widows and defunct male pensioners. Miss Roach, nearing 40, is a lonely singleton whose presence in the communal dining-room attracts needling comments from Mr Thwaites, a closet Nazi. He disapproves of Miss Roach’s friendship with an American lieutenant who happens to be black. ‘I spy a dusky combatant from distant shores,’ he says when the dashing officer appears.

Jonathan Kent’s production superbly evokes the complexities of wartime etiquette. Although the rules were stifling, they offered countless opportunities for subversion. When the buttoned-up Miss Roach invites the lieutenant to use her Christian name it feels like a sexual overture. And it is. Sharing a tumbler of whisky (very racy!), they contemplate taking a stroll by the riverside. Both are fully aware that consummation is being discussed. But Miss Roach’s romance is threatened by an exotic German rival, Miss Kugelmann, a sort of Teutonic Blanche DuBois, who intends to steal the American lieutenant but finds herself drawn to the wallet, if not the personality, of brutal Mr Thwaites.

Hamilton’s handling of character is so assured that his little suburban hotel feels like an entire society sketched in miniature. The casting is immaculate. Clive Francis brilliantly captures the brittle aggression of an ageing xenophobe whose heart is melted by an autumn romance. Fenella Woolgar (Miss Roach) conveys the first-night nerves of a smouldering virgin determined to explore her sexuality, if only to stave off her growing thoughts of suicide. Top honours go to the fabulous Lucy Cohu as the sexy German gold-digger whose predatory nature is inverted in the closing scenes as she turns from huntress into saviour. The handling of the story at the climax is breathtakingly swift and moving. Were there any justice in theatreland this terrific production would transfer immediately to the West End. But there is no justice, only money. And without a bankable star from Downton, Game of Thrones or Dr Who, this show may not outlast its current run.