People love telling secrets and spoiling surprises. We know it, and certainly trio The xx know it - which is why they've gone to so much effort to disguise the location of their MIF residency.

But the inner satnav of the most gifted geographer would even struggle to keep track of where this group of 60 spectators is headed as we sweep through underground passages and polytunnels to the featureless cube where The xx will perform the first of 18 intimate shows.

When we finally breach the inner sanctum and surround the band - stood anxiously waiting in the centre of the room - it's like some sort of indie heist. Front-duo Romy Madley Croft and Oliver Sim glance at the staring eyes just inches away from them; it's an arresting moment for all, like gatecrashing someone's bedroom rehearsal.

If they had a bedroom like this, mind, they'd probably have staged gigs there long ago. This purpose built, sunken stage, lit bright white from below, is what rock n roll dreams are made of, and having an audience standing six inches higher and all around them creates unforgettable drama.

Everyone is off guard; no one applauds, no one cheers, no one sings along. The band play on wordlessly in between.

In that uninterrupted silence, every intricacy of their powerfully personal songs is laid bare, every contact Romy's plectrum makes with the strings of her guitar clearly audible. And from Jamie "xx" Smith's table of gadgets and tricks, his tiny steel drum rings out like an instrument 10 times its size on opener Angels, Romy's emotional whisper of a voice dancing with it.

What this setting really provides, though, is a front seat view of that special bond between old school friends Romy and Oliver. They sing everything into each other's eyes, and as they simmer and strut through Crystalised, Tides and Unfold, they shift their microphones ever closer together until, by Chained, they're virtually nose to nose.

Around them, the white box comes to life: the ceiling rises, waves of light ripple around the walls, screens crash down revealing glimpses of the brick and concrete jungle our temporary stage is housed in, and then the roof falls down, screeching to a halt just inches above our heads.

It's the most electrifying music experience ever. And I want to go again, 17 more times.