Having never seen an episode of the hit Netflix series this prequel is based on, I was the perfect test case for whether it is a cynical exercise in 'fans-only' event theatre.

After three hours of goggling at the most technically advanced theatrical effects, including jump scares, and genuinely thrilling sequences, I am none the wiser about the mysterious powers that infect the teens of Hawkins, Indiana, or the explanation for The Upside Down.

But director Stephen Daldry is a superlative storyteller, pulling off a dizzying series of coup de theatre to bring writers Kate Trefry, Jack Thorne and The Duffer Brothers' dryly witty, engaging script to life. Set 25 years before the series, it also tackles darker issues about damaging parenting, post-war trauma, and the alienation of the outsider.

Ham & High: Joyce Bob and Hopper in Stranger Things The First Shadow at The Phoenix Theatre, West EndJoyce Bob and Hopper in Stranger Things The First Shadow at The Phoenix Theatre, West End (Image: Manuel Harlan)

Fans will love that the high school teens putting on a musical about witches in a funny play-within-a-play, are the younger versions of Joyce, (Isabella Pappas) Hopper (Oscar Lloyd) and Bob (Christopher Buckley) from the series.

But the performances, notably Pappas as its feisty director, have sufficient emotional heft that you are just as invested in her dashed hopes for escaping this small town.

The prequel itself has a prequel, a US naval ship involved in a WWII experiment that goes horribly wrong. Fast forward to 1959 and oddball newcomer Henry Creel (Louis McCartney) falls for adopted Patty (Ella Karuna Williams) just as strange static starts coming through the radio, and pets start dying horribly.

Ham & High: Henry (Louis McCartney) and Patty (Ella Karuna Williams) in Stranger Things the prequelHenry (Louis McCartney) and Patty (Ella Karuna Williams) in Stranger Things the prequel (Image: Manuel Harlan)

Our investigative trio go on the hunt, but the trail leads to Hawkins' lab presided over by Patrick Vaill's creepy Dr Brenner. (Even he gets a back story)

Magnificent work by lighting designer Jon Clark, and visual effects from Jamie Harrison and Chris Fisher allow the action to switch from Miriam Buether's evocative sets of faded Americana; a diner, police station, or gospel church, into jaw-dropping alternate worlds.

I confess I struggled to keep up with plot points, but I suspect the series thrives on half-explained mysteries, and this prequel was never going to answer everything.

Suffice to say that while fans will love being immersed in a familiar world, The First Shadow stands alone as a remarkable piece of theatre.

Stranger Things is at The Phoenix Theatre, West End until further notice.