Whether or not a West end production would utilise the technique’s full dramatic potential, chances are it would have the budget to overcome some of the technical issues that blight the Almeida’s production, Slung Low’s Last Seen.

The company use chunky ear-defender type radio ‘phones and miked-up actors to ensure that even those in the audience who can’t see the action can at least hear every nuance of the dialogue. A sound tech accompanies the procession around the streets of Islington, armed with a bulky backpack that broadcasts incidental music and sound effects to accentuate the actors’ voices or underscore silent sequences. The technology vastly improves the outdoor promenade format, helping maintain an atmosphere that could otherwise easily be shattered by background noise.

There are three routes, and each audience member only gets to see one, but occasionally you can catch glimpses of set pieces not intended for you: a fully laid dinner table through a park gate is a reminder that the stories you see are never the entirety of what the city has to tell. Every passer-by wearing headphones or a hands-free set feels like they could potentially be a player. Though all you ever do is follow and listen, there’s an exciting sense of exploration and discovery without the attendant dangers of the unknown.

But – and though it most probably isn’t the company’s fault, it’s still a big but – the headphones pick up interference far too easily. Some of the dialogue sinks under waves of static, which can be physically painful on the ear, and the music under one potentially very poignant moment has to share the airwaves with a local pirate radio station broadcasting from a nearby window.

The technology is simultaneously the best and worst aspect of Last Seen. Without it, the production would be at best pedestrian and at worst inaudible. Because of it, the production will be discussed more for its technical flaws than for its dramatic merit (as I’ve demonstrated). What the production definitely is, though, is a glimpse of how the technology could positively impact theatre, whether as a dramatic technique in itself or as a facilitatory tool, once its shortcomings are ironed out. The theatre world might just have to wait until the technology catches up to its vision.

Participants wired up with headphones and mp3 players are released in pairs into the supermarket, where a voice guides them gently through the aisles towards a playful encounter.

Every effort is made to put potentially nervous participants at their ease, from the reassuring notice in the BAC foyer (“to the people around you shopping at the supermarket you’ll look just like any other shopper”) to the soft, friendly choice of guide voice. Still, it’s sometimes hard to avoid panicky thoughts like, Is this voice going to order me to shoplift, or talk to a stranger, or pay for these random items in my trolley? And will it wreck the preordained choreography of the performance if I refuse?

The head-bendingly precise timing necessary to keep both participants in sync hampers the eventual face-to-face interaction; because every smile and awkward downward glance has to be exhaustively narrated, fleeting glances telescope out into lingering stares, and small actions expand and decelerate into pantomime. But when not mired in minutiae, Wondermart yields some perfectly orchestrated moments, such as when both participants tail each other, mirroring one another’s movements from opposite ends of the same aisle. I defy anyone not to crack a smile when peeping surreptitiously around the end-of-aisle display to find a face peeping surreptitiously back from the other end.

Compared to Rotozaza’s intense GuruGuru, Wondermart is pure whimsy; but it proves that the company aren’t content to coast on the novelty value of audio-instructed autoteatro. It’s still a relatively new form, but far from treating it like a newborn, Rotozaza are relentlessly shaking it about, turning it upside-down and bolting new bits to it like a bunch of theatrical mad scientists. As Aristotle put it: “No great genius has ever existed without some touch of madness.”

While I decide whether or not I’m in a giving mood, here are the publicly available facts. Tunnel 228 is a free but limited capacity art-exhibition-cum-theatrical-installation, the result of a collaboration between Punchdrunk, the Old and Young Vic theatres and a selection of contemporary artists. Booking had been open, but kept hush-hush, for four days when The London Paper gave the game away, prompting the remaining slots to book up in a matter of hours.

While I disagree with Matt Trueman’s suggestion that the freesheet’s article invited undeserving participants to the event, for three reasons – a) it smacks uncomfortably of elitism and arbitrary judgments of ‘worthiness’ to experience art; b) the article was an innocuous one on page six that would most likely only have appealed to Punchdrunk fans anyway; and c) his notional ‘deserving’ fans had a four-day headstart – he does make one vital point. Tunnel 228 isn’t meant to be found (i.e. stumbled upon at random); you’re meant to find it (i.e. actively seek it out).

The booking site, disguised behind a tacky frontpage advertising a rail cleaning service, is difficult to find unless you know you’re looking for something (if not exactly what that something will turn out to be). The entrance to the venue is nearly impossible to locate unless you’ve found the website.

Even once you’re inside, there’s no guidance to be had from the stewards: they’re mute unless they’re telling you what you aren’t allowed to do. The onus is on you; on your self-motivated voyage of discovery. Will you attempt to figure out the origin and purpose of the Rube Goldberg machine? Hunt down the man immortalised in mural form on various walls? Seek out all Slinkachu’s miniature dioramas? Or just make it your mission to explore every corner – even the ones you’re not sure you’re allowed in?

That’s all I’m giving you in the way of hints. You’ll thank me if, as Old Vic Artistic Director Kevin hopes, the tunnel reopens in the autumn, and you can experience the thrill of discovery unspoiled.

It may be that any journey past Execution Dock is made in the company of Captain Kidd’s ghost, but I had already begun to ‘be’ in the performance well before I arrived at the venue – an imposing five-storey building in Wapping Lane. The dreary industrial architecture alone was enough to suggest that here I was indeed going to witness a pact between Man and Devil.

Glad to get out of the bitter cold, I was ushered downstairs to a bar seemingly run by ladies from the American deep South, uneasily stuck in some 1920’s hayseed and moonshine dream. It was in the men’s toilets of this establishment that my belt fell to pieces. This is actually due to wet rot in my house but you could be forgiven for seeing the hand of a wayward spirit at work.

Holding up my pants with one hand and feeling a little cold, the group I had joined was then dropped off in small groups on each of the five floors by a swaggering, drunk preacher whose dirty linen suit spoke of restless nights alone with a bible and a whiskey bottle.

By necessity, the details must stop here. What happens beyond the lift doors is largely up to you and the performers. Certainly a main story arc will guide you, but like Dr Faust’s search for the true essence of life, the performance is not a passive transit from one point to another: part of it lies beyond our comprehension. This is the slice for the Gods as Ernst Junger once described the hidden face of war.

Not that Punchdrunk purposefully indulges in obfuscation to the point that the performance is only a journey into the unknown. Key episodes from the myth of Faust have been isolated and developed and iconic cultural references have been woven into the physical appearance of the rooms, corridors and stairwells of the building.

This is perhaps where I would sound the only note of caution. It felt at times that the use of space threatened to veer into the absurd and was perhaps more in keeping with a theme park than as the physical matrix required to support the performance. The sheer size of the building is certainly an issue as is I suspect the amount of money needed to exploit such a space.

At the same time, the space is what contributes to the impression of being lost in a place that holds no memory or ego. Although it is clearly a story about ‘self’, it is not our own ‘self’ and that can be either a blessing or a curse.

A blessing because for a moment I forgot the dangerous farce that is life in London, and a curse because it asks the sort of question which theatre (nor anything else seemingly) cannot answer.

Go see it. That is all.