Go to [SPOILERS REDACTED] Station. Bring a charged up phone, headphones and a coat. Try to remain inconspicuous.

With this email begins the latest immersive theatre experience from the founders of Shunt. Wiretapper is an hour-long event that requires you to roam around London locations while listening to your smartphone. Something we all do every day, right? Even that person walking past you right now. Maybe they’re involved in a theatrical event as they do so.

Or maybe that person who’s dressed a little oddly, who’s behaving a little eccentrically, is part of a larger narrative that’s going on around you right now. There’s no doubting that taking part in a Wiretapper performance, which starts off on a railway concourse and moves to take in several London landmarks, makes you wonder who is part of the event and who is not. And that all adds to the fun.

At the appointed hour (in our case, 7pm on a bustling Friday evening) we hit the play button on the previously downloaded Wiretapper app. At first, nothing seems to be happening – you’re hearing the hustle and bustle of a commuter hub, the clipped tones of the station announcer occasionally wafting above the hubbub.

And then she starts talking to you.

Your “handler”, a male voice who gives you some instructions, tells you to look out for a woman in white, carrying a guitar case. And there she is, strolling across the concourse, after which you are given five minutes to get to the next waypoint.

And it’s in this open space that the paranoia begins to creep in. Is that sign saying “CCTV is in operation” a prop? Is that a tourist, or a terrorist? And where did the woman with the guitar go?

The story unfolds predominantly on audio, although it soon emerges that there are indeed characters among the crowd. As part of the inconspicuous nature, we hang back, allowing the characters to mime to the prerecorded audio as if we are eavesdropping via covert surveillance methods.

After another location change, there is a denouement. This is the point which, for me, felt a little too hokey: after laying the foundations of a spy thriller, the conclusion is rather firmly placed in a different genre entirely. But as it is only an hour, and so unlike any other form of theatre you’re likely to experience this year, that hardly matters a bit.

Wiretapper continues until June 21. Times vary. To book, download the app from the Wiretapper website.