Giallo comes to swinging London in Edgar Wright’s latest genre-fried runaround, a sparky entertainment whose tricksy, hop-scotching screenplay sadly fizzles out by its final act. You could easily spend the entire word count of a review listing all of the cultural references that have fed into the creation of Last Night in Soho, but let’s just stick to two for now: the first is Wes Craven’s Nightmare on Elm Street, for the simple fact that this is about a young woman who begins to experience a worryingly tactile version of her dream life; and the other is Roman Polanski’s Repulsion, a classic London movie concerned with the creeping terror of unchecked male lechery.

Thomasin McKenzie stars as Eloise, Redruth’s most promising fashion designer with an invite to live out her dreams by studying in London. After quickly discovering that everyone in her dorm is an unbearable rah-rah, she decamps to the attic studio in the crumbling Fitzrovia stack of lovably doddery Miss Collins (Diana Rigg) who appears to cherish Eloise’s wide-eyed innocence.

It is then that our heroine begins to experience lucid nighttime visions of a glamorous and confident cabaret dancer named Sadie (Anya Taylor-Joy) who struts her stuff in the ’60s dancehalls and clip joints of Soho – visions Eloise accepts as the result of her love of pop music from the era. Yet as the nights tick on and Sandie’s story unfurls, things aren’t as hopeful as they initially seem. Is Sandie a representation of Eloise’s suppressed id, a vision of her outgoing potential? Or does she stem from somewhere else entirely?

There’s that famous scene in the Marx brothers’ comedy classic Duck Soup where Harpo pretends to be a mirror image of Groucho by perfectly mimicking his movements. This trick features heavily in Last Night in Soho, as Wright flexes his considerable technical muscles by having Eloise and Sandie constantly switching between the foreground and a background mirror image. These subtle special effects are pulled off with amazing precision, and you really have to pay attention to who’s centre frame and how that plays into its complex, identity-toying storyline.

The set-up is fun and compelling, the soundtrack is rammed with bangers by Cilla Black, Petula Clark and The Kinks, and McKenzie makes for a breezily empathetic lead. And yet there’s a point where the story jumps the shark, and suggestions of a deeper, more mature study into the workings of the mind, the architecture of dreams and even the dynamics of depression amount to little, as Wright and co-writer Krysty Wilson-Cairns lean far too heavily on the hoary whodunit? clichés that are baked into the DNA of the giallo<e/m> genre.

The film is at its best when holding back details and sculpting fine character details, but the intensity is ramped up far too early and it becomes increasingly tough to take the plot seriously, or build an emotional connection with its climactic revelations. That said, there’s enjoyment to be gleaned from the lovely location shooting which takes in the length and breadth of Soho while centring around beloved Irish boozer, The Toucan. Also, the film is movingly dedicated to the late Diana Rigg, and this is most definitely a plum swansong for the ’60s icon.