All the world’s a train and all the men and women merely passangers

9.46pm on the Northern Line. Almost home. I’m staring at an advert about match.com above a sleeping granny’s head, expecting a crowd of Islington hipsters to slide into seats and wake her up. No one appears to get on the tube at the next station.

The train pulls away and the iron screech of wheels upon tracks is strangely reassuring. I look along the carriage and barely register a man in a Batman costume. He strides over, sits opposite me, pulls out a copy of Hello magazine. ‘Another student fancy dress night,’ I think. He makes no eye-contact with anyone. He just sits there, flicking through his magazine.

The train lights flicker for a split second. The train slows down and the scenery goes from darkness into light as we move into the next station. The granny wakes up because she’s dropped her umbrella. She notices Batman and giggles. Suddenly, the infamous Nokia mobile theme tune breaks the silence of the carriage – baffling as we are underground. ‘Hey Robin…what’s that? Holy sardine!’

A long, loud wail and then – ‘Good evening ladies and gentleman. We are tonight’s entertainment!’ Loud rap blasts out of nowhere and the (previously unseen) Joker springs up from the corner of the carriage. The granny yelps, then giggles again. The Joker walks up to Batman, takes his measure and the fight kicks off. Batman aims vicious punches at the Jocker who responds with a sharp kick to the leg.

Holy Smokes Batman

Then, as if everything was just a dream, the movements fall into slow motion and the music stops. The Joker tumbles to the floor and, as the train pulls into the next stop, he drags himself, weak and defeated, onto the platform. The train moves off and his purple suit flaps in the wind. I turn to see if Batman is standing there, savouring his moment of victory. He is nowhere to be seen.

It quickly struck me that the granny and I had witnessed our own private session of performance art in the time it had taken to travel three stops. At first it seemed that it had been surreal and instantaneous – as if we had unwittingly been caught in an improvised narrative sequence.

Then I realised quite how ‘staged’ the performance had been; the phone call, the synchronisation with each of the tube stops, characters appearing from nowhere. This was one of the cleverest instances of performance art I had ever seen. It relied entirely on an audience being captured unaware but becoming immediately complicit in a context and a storyline.

The characters merged reality and make-believe so well that, on surfacing to street level, it felt as if life had come straight from a comic book. Maybe that’s the ambiguity that the performers wanted. They left no names or traces. It only happened because we were on that tube, in that moment. It was such a gripping experience of pure illusion – it even managed to keep granny awake.