London has a brand-new theatre – yet again. Last summer, a cabaret venue opened in the Haymarket for the first time. More recently, the Marylebone Theatre near Regent’s Park held its debut show. And now Nica Burns of Nimax Theatres has announced a new venture, @sohoplace, which she says is the first West End venue to open for 50 years.

The playing area is a hoop-shaped enclosure with rising tiers of seats overlooking a deep oblong pit. Cage fighting and mud-wrestling could be staged here to great advantage. The poster for the debut show, MARVELLOUS, features the title in bright pastel letters with a yellow balloon, a pair of clown’s shoes and a perky budgerigar.

The image suggests a heart-warming children’s comedy or a feelgood high-school musical. In fact it’s a biographical play about a working-class oddball, Neil from Newcastle-under-Lyme, who led a peculiar life as a casual labourer. His story unfolds in a series of vignettes. He inherits minor cognitive and physical handicaps which expose him to bullies at school. His mother asks him about his future and he announces his plan to become a clown or a vicar. He achieves both ambitions. He wants to study at Keele University but rather than applying for a place, he simply shows up on campus each day and turns himself into a regular fixture. (A smart move – no fees to pay.)

He’s employed by Stoke City Football Club as a boot-polisher and a mascot. He joins a circus. He becomes a minister. He seeks autobiographies and bags the signatures of Harold Wilson and Kevin Keegan. Do you get the idea? The show is a list of actions which don’t add up to a drama. Neil bumbles through life, like Zelig or Forrest Gump, observing events without affecting them. We’re never told what great mission he hopes to fulfil.

There’s no jeopardy or surprise, and no sense of a life-changing crisis or a grand emotional struggle. As you watch Neil’s biography you hope that he finds a safe route through his troubles but you don’t care if he fails. It’s an unusual theatrical experience – like arriving by mistake at the retirement party of a gardener you’ve never met. Director Theresa Heskins has encouraged the actors to improvise bits of business and to invite the crowd to laugh, clap wildly and join in the fun. Some will find this a chore. It depends on your willingness to pay for entertainment only to learn that the entertainment is you.

At press night, the audience had a good time but the kids seemed to enjoy things more than the adults. It was quite a starry affair. Melvyn Bragg chuckled genially throughout. Andrew Lloyd Webber, with a faint air of impatience, read his programme twice, as if memorising its contents for an exam. This production has been deliberately chosen to open the new venue. MARVELLOUS is an antidote to the star-driven, award-laden, money-spinning shows that infest the West End. The character of Neil doesn’t need a profoundly moving narrative. It’s enough that he exists. Nimax Theatres have plucked an English eccentric from obscurity and crowned him king for one night. In a way, it’s a tribute to the monarchy.

Peter Gill, aged 83, has produced a one-act play, Something in the Air, about the gay scene in London during the 1950s. The timeline shifts between the testimony of two ageing crocks, Alex and Colin, and their alter egos as lusty youngsters. The pairs of lovers are separated dramatically, and physically, so the play feels bitty and disjointed. It’s hard to get a handle on anything. The old queens are so frail and doddery that they can’t possibly have a dramatic challenge to overcome. Surviving the 70-minute running time would be a major triumph.

Both elders are cared for by handsome younger relatives, Andrew and Clare, who start the most delicate of flirtations but their affair seems unlikely to go anywhere. This is a highly specialised play full of cultural references that will puzzle anyone under 50: cod liver oil, Aldermaston, Chez Victor, Lord Woolton, Mario Lanza, Marghanita Laski and so on.

The coarse sexual language used by the lovers feels out of place. In the 1950s it was doubtless liberating for homosexuals to speak openly about their illegal desires but now it’s unseemly to hear venerable pensioners describing their couplings in Anglo-Saxon crudities. It sounds puerile. The show may struggle to find an audience. Only the truly ancient can recall adult life in postwar London and this show aims at a subsection of that small and dwindling group. It’s for posh, left-wing gay men who discovered romance in Bloomsbury 70 years ago. Anyone who wants a ticket will have one already. The rest are dead.