Actor Jack Holden is no stranger to the West End. His first job out of drama school was as the lead (human) character in War Horse. This then is his West End debut as a writer/performer in a solo play he literally dreamed up while in lockdown last year.

The main inspiration for his whirligig, musicalised monologue (with accompaniment on stage by composer musician John Elliott) is the time he spent nearly a decade ago when at the age of 22 he was working as a volunteer for Switchboard, the LGTBQ+ helpline.

One call in particular led to the dream and this play. It was from a middle aged chap who had a story to tell about his life in Soho during the 1980s, a period in which a new, deadly illness emerged chiefly among gay people.

Alone at his workstation, Holden segues between the role of nervous listener and confident caller. The former is a version of his diffident, younger self; the latter is Michael — gruffer and wiser and partly motivated to speak by young Jack’s scepticism that someone his age knows what a good night out is.

The story recalls a Soho of decadent dives and also a gay community in the square mile that is now largely lost, it is said. As Michael, Holden paints a vivid portrait of the place, its people and the clubs and bars that became his haunts and refuges. One is a karaoke club in which he meets Dave with whom Michael forms that very rare thing among his peers of DJs, clubbers, and hedonists — a relationship. This ideal is cut short when the couple are diagnosed with HIV and given four years to live.

There is nothing like a ticking clock to give a story momentum and tension. But here the countdown smashes head first into a logic problem that despite the bravura of Holden’s performance is impossible to ignore.

Without giving too much away, the climax demands that we accept at face value Michael’s belief that his life will end four years to the day after his diagnosis. It’s a belief that informs his every action and emotion right up to midnight when his drug-fuelled body collapses at the expectation of death, much as if Michael had been the victim of a fake execution.

But HIV is not a gun loaded with blanks. So why Michael should believe his death is imminent when his body has the energy to party like there is no tomorrow is never explained. We can only assume that writer and director Bronagh Lagan sees it as convenient dramatic device.

It’s a shame because, from not much more than a shadowy stage and simple scaffolding Holden vividly conjures a Soho as brimful of humanity as it is hedonism. The scene in which he morphs into worldweary drag queen and, with HIV on the rampage, performs Is That All There Is? — Leiber and Stoller’s hymn to disillusionment — would not be out out of place in Cabaret’s Kit Kat Club. And who would not want to buy a socially distanced ticket for that?