Joshua Kaplan’s play starts with an amusing conceit: Daniel Radcliffe, Emma Watson and Rupert Grint are staging an intervention to force an end to what one calls JK Rowling’s “transphobic bullshit” on X. They meet the Harry Potter author in a swanky London restaurant, hoping to reach if not agreement, then at least a cessation of hostilities.

It begins with noise: a social-media cacophony of voices drowning each other out. Kaplan’s play is an attempt to cut through the din; to see if a reasonable conversation is possible about a polarising topic.

The production, by Civil Disobedience and Theatre of the Existential Void, has already caused a stir thanks to a dispute with Peter Schaufuss, owner of St Stephen’s churchwhere the run was initially scheduled. Now at the Assembly Rooms, it is less likely to incite audiences with its subject matter than with its dreariness.

Terf (the acronym for trans-exclusionary radical feminist) could have been a fiery exchange of fiercely held viewpoints. Only rarely does it get anywhere near that. The single explosive speech by Tom Longmire as an otherwise head-in-the-clouds Rupert and the one impassioned broadside by Trelawny Kean as a book-learned Emma are not enough to kickstart the drama.

That is especially the case when the opposing view is held by a weirdly posh Rowling (Laura Kay Bailey), too haughty and short-tempered to allow discussion to flourish. We meander back in time to see examples of the author’s troubled history with men and her substantial charitable donations (which surely cannot have been as begrudging as they seem here), but we see nothing to connect this generous liberal-minded novelist with her divisive social-media output.

There is no conflict, just mutual irritation. Piers Mackenzie as Daniel is as fractious as the rest of them, in a clunky production that is as high on good intentions as it is low on impact.