It’s getting silly now. London’s subsidised theatres aren’t just competing to put on the worst play of the year but to create the worst production of all time. The Young Vic’s new effort, Conundrum, is an impenetrable rant which even the Guardiancriticised.

The Royal Court enters the fray with Alistair McDowall’s The Glow, directed by Vicky Featherstone. Act One is a flatshare sitcom set in the 19th century and features a pompous spiritualist, Mrs Lyall, who forces her chippy son, Mason, to live with a lunatic called Sadie. Mrs Lyall purchased Sadie from an asylum and together they conjure up a host of ancient spirits including an angry Jesus figure who has a sword and an Irish accent. Drippy Sadie doesn’t get on with Mason, a petulant halfwit driven nuts by his hectoring mother.

Everyone hates each other. Mason sees Sadie cuddling his teddy bear. So he rips it to pieces. Violence takes over. Mason starts shoving Sadie around the drawing room and when he suffers a nosebleed she gives his conk a savage twist. Mrs Lyall, who holds a black belt in aikido, gets Sadie into a complicated arm lock and snaps her hand in two. CRUNCH goes the soundtrack. But the wound heals thanks to a miraculous light which enables Sadie to travel through time. End of Act One. It’s so bad that the BBC could easily turn it into an award-winning series watched by nobody.

In Act Two, Sadie time-travels to the 14th century, and then to the stone age, and then to the 1990s. She meets no one of interest. This isn’t surprising as she’s a characterless airhead with the IQ of a heart valve. She spends a lot of time with the angry Jesus figure who works as a freelance knight. When he hurts his leg in battle, she bandages it. And she meets a university lecturer in green clothes who tells her stuff.

These boring scenes are perked up with fancy projections and Wagnerian sound effects. Distractions such as this often indicate an anxious director who knows that the script is a dud and wants to bamboozle the crowd with flashy extras. The show’s crowning horror, the set by Merle Hensel, is a rusty angular bunker that looks like a bikeshed designed by the Soviet Union’s most successful brutalist.

What’s the point of this artless waste of resources? There’s no good reason why pretentious philistines at the Royal Court, and the Young Vic, should be allowed to despoil the public purse with fraudulent tripe. Supporters of subsidised art, who tend to be its beneficiaries as well, claim that state funding helps the UK to maintain its position as a global leader. But we have numerous cultural exports (the Beatles, the Harry Potter series, the James Bond franchise, Andrew Lloyd Webber) that rose to dominance without a penny of government aid. Subsidy supports the third-rate. Killing one will get rid of the other.

Hollywood seductress Ava Gardner is brought to life in a new show by Elizabeth McGovern, who also takes the lead role. Her script is based on the book The Secret Conversations by Gardner and Peter Evans. McGovern is still beautiful enough to play the star in her prime but she prefers to give us an unflattering portrait of an ageing foul-mouthed wreck, recovering from a stroke and padding around her apartment slurping whisky. The script teases us with gossip that no one cares about any more. How long was Frank Sinatra’s penis? The issue is discussed but the answer is never supplied.

A similar problem affects the relationship between Ava and Evans who professes his love for her early on. Wow. A biographer smitten with his subject. Fascinating. She’s an ageing sex goddess and he’s a thrusting young literary lion. What could happen next? But their romance gets shunted aside because the play has to rush off and look into Ava’s relationships with Howard Hughes and Mickey Rooney. There’s not enough space for the romance with Evans. So why mention it? A play must honour its promises.

The production centres on Anatol Yusef who has to play four supporting roles. Physically he’s short and dumpy, and when he impersonates Sinatra — one of the great style icons of the 20th century — he’s given a black T-shirt and slacks to wear. He looks like a Van Morrison impersonator busking outside Nando’s. The budget can’t even stretch to a £65 washable suit from Primark. And putting a trilby on his head doesn’t make him Sinatra either.

It’s a shame but not a disaster. With a fresh script, a larger cast and a general re-think this show could fly. The star, McGovern, should don a wig and frock and give us Ava in her sexual prime. That’s what the audience wants to see, not the maudlin ramblings of a broken lush crawling towards death.