I have signed documents, I have been told to go to secret locations and I am meeting people I do not know. I have registered online and been told that I am not me, but I am in fact Luca Mynott, Galactic Explorer, and that I should wear a certain scarf, and bring some seeds for currency. And now I am standing outside a London tube station wondering how the simple pleasure of seeing a movie has ballooned into this.

This is Secret Cinema, which turns a night at the flicks in to an immersive, participatory, full Technicolor live event. In seven years it had gone from niche pursuit – a screening of Gus Van Sant’s Paranoid Park to 400 people in a railway yard – to major cultural player, with more than 40 events, including screenings of Terry Gilliam's Brazil and Ridley Scott’s Prometheus, bringing in 35,000 punters or more.

Last summer Secret Cinema pulled off their biggest coup to date, selling 85,000 tickets for a lavish Back to The Future jamboree that created an entire Fifties American town in East London, complete with (real) hair salons and a high school prom.

But this year’s show is set to send them stratospheric – Star Wars: The Empire Strikes Back, sees Secret Cinema gunning for the biggest movie franchise of all time. They’ve netted the second original Star Wars film, made way back in the blissful days of 1980 before computer effects ran riot across the franchise, and one which many Star Wars fans deem the best.

In it we meet backwards talking sage Yoda, there’s an epic battle on the ice planet Hoth featuring giant AT-AT Walkers and hero Luke Skywalker finds out both that Princess Leia is his sister and that the greatest sci-fi villain of all time, Darth Vader, is his father.

Secret Cinema has assembled a formidable creative team to take on the Star Wars mythology. One of them is technical director Piers Shepperd, who worked with Danny Boyle on the 2012 Olympics Ceremony. Why, I wonder, would a man of Shepperd’s CV want to be working on Secret Cinema – something that only a few years ago was just a bit of fun?

Stormtroopers prowl around the set of Secret Cinema's The Empire Strikes Back Credit: Al Overdrive

“The proper answer is it’s the future. I’ve done concert tours, the West End and some very large scale festivals. This is more exciting. In the West End you sit down, pay for your programme, queue at the bar for your interval drinks, then you watch a show. You know pretty much what you’re going to get. Every now and again you see something which is different. But nothing compared to what we’re trying to do here in terms of either technical or creative ambition. The audience just don't know what to expect.”

And I don’t either, yet knowing I am about to be granted early exclusive access to the best-kept secret of the summer has me stupidly excited. Soon, I am escorted into the car park of a vast, disused warehouse. My guide is Fabien Riggall, Secret Cinema’s creative director and founder, the PT Barnum of the whole shebang. Mobile phones are sealed in silver bags. Then I am smuggled aboard a cargo transporter and with some clever animation on a wraparound screen, I am taken to a galaxy far, far away…

As I step in to the first of a series of huge sets, all immaculately conceived and fully dressed, I feel like I have arrived in Marrakesh’s medina. Stormtroopers are on patrol. R2-D2 trundles past. Stalls are selling artwork and some (good) food. One hut is a gambling den, showing pod racing – a nod to one of the Star Wars prequels. Next door is the infamous cantina, serving themed cocktails, thronged with aliens and humans.

The format of the evening feels freeform but as with any great movie, there are key moments that you wouldn’t want to miss. When I spy a full-size land speeder with C3P0 doddering behind it, for example, I know I should follow it to see who’s inside. The two or three hours leading up to the screening of the film feel like a music festival in the lead up to the main act, except you’re not just the audience, you’re a player too. Everyone, from the bar staff to the front of house to the toilet attendants, is in costume – 300 bespoke outfits have been made by 40 different costumiers – and they are in character too.

Secret Cinema is meticulous about everyone doing several hours’ rehearsal beforehand. Because these actors know what character every audience member is too, interaction is seamless and convincing. At one point I find myself chowing down on a falafel wrap while conducting a back-alley trade with a man in a cassock – Alpha Martinez, bounty hunter – I’ve never met. I genuinely don’t know if he’s Secret Cinema staff or just another punter.

The site itself is vast, 18 acres of it split into several different zones. In three months Riggall and a team totalling over 400 people has designed and constructed an entire world, taking in everything from industrial tech to desert souks. One hundred and eighty different artists have been booked each night to play music, act and interact with an audience that could top 100,000 over four months. There are 40 market stalls, art galleries, street food, three bands a night playing in the bar, five different stages.

A miniature Darth Vader at Secret Cinema: The Empire Strikes Back Credit: Camilla Greenwell

This doesn’t come about by accident. Backstage there are Performance Timelines on the wall for "Project Rebellion" that show how the flow of costumed punters from one room to the next is carefully choreographed. There are intricate drawings that reveal areas – secret nightclubs; resting pods for a lie-down – that I never saw on my way to the final destination of the screening room itself. There are teams for curating music, production design, a costume department – who were fitting out a 7 ft Chewbacca when I passed – and an art department.

Riggall shows me round his giant playroom with obvious pride. “It gives me great pleasure after last year to mention that we are very much finished and ready,” he says. “Oh s--- – I didn’t mean to bring last year up.”

“Last year” was the first misstep in what to that point had been a gleaming procession for Secret Cinema. Their Back to the Future show made headlines for all the wrong reasons when, with more than 50,000 tickets sold, the first performances were postponed at the eleventh hour.

“We were working in the Olympic park and it was a very complicated set up,” says Riggall. “There were complications which I can’t even go in to.”

Why not?

“I don't want to scupper the ability to keep doing things,” he says, evidently aware that burning bridges with whichever authorities permit him to take over vast abandoned buildings is not a good idea. “You just need to keep going. Occasionally bad things will happen.”

A Secret Cinema actor waits in the wings Credit: Camilla Greenwell

To his credit he didn’t quit after that, he simply set his sights higher. From the outset Secret Cinema Presents The Empire Strikes Back has been ambitious, not least in trying to screen George Lucas’s defining blockbuster in the first place. You don’t need to know much about the movie business to guess that Disney and Lucas guard the rights to their greatest moneyspinner, the franchise that invented merchandising, ferociously. Riggall says getting a license from Disney took the best part of a year. “I’m very tenacious. We’re an exhibitor like any other so when we do a film, yes, we pay a license fee like anyone. They’re protective – they want to make sure – but actually really helpful. Now, no more financial questions.”

As that suggests, Rigall comes across more as dreamy aesthete than hard-nosed businessman. He’s happy to talk about Secret Cinema as a new type of cultural node, whereas he finds questions about the £78 ticket price less enjoyable.

“People talk about the ticket being expensive,” he says. “I could go in to the detail of what we’re spending the money on – the animators, sets, specifics – but if I give those things away it will ruin it. That’s why it’s so frustrating. But the price of the ticket? I’ve put it into… this,” he says spreading his arms.

And when it finally comes to watching the film, you realise that the preamble, the dress-up, the blurring of boundaries between audience and actors, dramatically enhances the pleasure of seeing the film. My night as Luca Mynott, member of the Rebel Alliance, didn't just put me in the mood to watch The Empire Strikes Back for the umpteenth time, it made me feel like I was part of the story. I whooped and hollered with the best of them as Luke and Darth fought it out. “Search your feelings, you know it to be true!” as Darth says. And I believed him.

SECRET CINEMA Presents STAR WARS: THE EMPIRE STRIKES BACK takes place from June 4 – September 27 www.secretcinema.org/tickets