On an unassuming grey door on the concourse of London Bridge station, there's a sign: "No access to Shunt." To most commuters, if they notice it at all, it will mean nothing. For a lucky few, however, passing that door brings a rush of memories. For five years, the damp, brick railway tunnel hidden behind it was home to one of the most vibrant, cult performance venues in London: the Shunt Vaults.
Extraordinary occurrences were commonplace, not least in Shunt's own large-scale promenade theatre productions. Feathered showgirls rode in on hearses. Fencers duelled on the walls. Briefcases spontaneously combusted. "An orthodox Jew on a foot-cycle. A nun on a spacehopper," adds David Rosenberg, one of Shunt's 10 co-founders. "We don't know what these images mean either, but we'll find something strong, something funny or peculiar, in them that interests us."
Having abandoned the tunnels in 2009, the collective set up home in an old tobacco warehouse on Bermondsey Street. Now, in a former biscuit factory down the road, they will open their first new show in three years. The Architects, which opens tonight, is a freewheeling riff on the Minotaur myth, which will be staged in a specially constructed "disorientating labyrinth". "It's a simple story that everybody knows," says Rosenberg. "But looked at from other perspectives, the Minotaur essentially becomes propaganda, which leads onto fearmongering and what it would take for a country to sacrifice their children. It's the idea of the bogeyman – be it communism, fundamental Islam, rioters. Our society runs on fear."
Beyond that, the company is keeping schtum. One curious detail has emerged, though: there will be a "sex machine". In the myth, King Minas's wife is besotted with a white bull and commissions a contraption to enable consummation. "With the historic reference and our puerile interests, it seemed a shame not to bring it into the piece," says Rosenberg.
This is Shunt's way: to hurl an audience into a headspin. Their performances are expansive, hallucinogenic journeys, teeming with twisted pop cultural references and laced with an absurd, satirical bite. "We try to interrupt an audience's expectations," says Rosenberg. "The worst thing is an audience that knows what's going to happen next."
While the internal logic can make Shunt shows seem nonsensical, politics always permeates. Dance Bear Dance (2003) referenced the war on terror. Their last show, Money, touched on the financial crisis. "Now, we find ourselves in a period of enforced austerity with the idea of Europe being challenged and Greece taking a battering," says Rosenberg, "Because our shows don't aim at a preconceived end-point, they're malleable to current events."
For Shunt, meaning is always secondary to experience – too secondary for many critics, who have deemed "whatever you want it to mean", a cop-out. "Confusion and bafflement" is a deliberate ploy, argues Rosenberg. "We've failed on occasion and made something that's simply baffling, that's slipped into impenetrability."
It's in stark contrast to a certain type of voguish interactive theatre (Punchdrunk, say), a mode Shunt are keen to distance themselves from. "It's often a bit like those Choose Your Own Adventure books," says Louise Mari, another co-founder. "You appear to have choices, but they're all much of a muchness. Those shows are prescriptive. They expect a reaction."
"The audience have very little choice in our shows," agrees Rosenberg. "They can't choose not to see things or walk away. They can't really leave – it's a labyrinth, after all – which can make people quite anxious. In some ways, it's about being taken hostage."
'The Architects', The Biscuit Factory, London SE1 (020 7452 3000; national theatre.org.uk) tonight to 2 February