The swarthy man lumbers up the concrete staircase, the mob I'm part of only a few steps behind. He reaches the top and turns, a hand outstretched in defiance, out of breath and forced to fight. The mob closes in.
"Weren't you in High School Musical?"
But he speaks at the same time, also mistaking us for celebrities. It's a draw. If he'd complemented our eyes our game would be over; if we'd sung him a song we'd have been the victors.
The ten-second amnesty expires and he's gone. Minutes later he returns by another route, sniping us with a compliment before the unwieldy group can react.
It's Cruel To Be Kind, part of the Hide & Seek Festival, which is kindergarten for adults. I'm part of such an enormous group because of a spectacular scene a few minutes before: two medium-sized groups spotted each other in jubilee park and charged, screaming compliments like battle cries as our lines collided. Even the South Bank's jaded pedestrians turned their heads for that one.
Not all the games involved running. But the good ones did. Checkpoint saw a team of smugglers challenged to move the contents of a living room from one side of the centre to the other, past half a dozen guards posted around the edges of the safe zone.
Most of the gear went under jackets, or over the balcony, handed down to a 'clean' contact on the inside. We shifted the chair using the usual method, passed down by repeat players: the Chair Rush. A dozen smugglers grabbed chairs, eleven of which were clean. I got through, but I didn't have the real chair.
It was moving the body that was the real problem. We sent a decoy though in a wheelchair. We had spotters using mobile phones, "civilians" chatting to the guards, an actor taking a dive on the stairs while the smuggling team took a little-used lift. And they still intercepted her.
A co-worker passed me while playing an immersive GPS-based game on a PDA. He didn't even see me wave. The game itself is excellent, though not exceptional: more exciting is just how easy it would be to make one, now.
Full immersion is still a problem. I think this is a skill that needs to be trained and kept current like any other. In the preceding conference, somebody asked about helping children to create their own Alternate Reality Games; the presenter responded with "I think they already do". He was right; what we're ultimately trying to do, with all this organisation, all this technology, is to return to the days of "I'm a fire engine".
Oh, and the zombies are coming. Seeing the poster innocuously placed with theatre fliers was one thing, but finding a business card stuffed into the side pocket of my backpack was a total TINAG moment for me. This is one region where I'm still a new player, and the experience still dominates the content. Deep down, though, I don't want to play games. I want to make them.