Seventy-five students, three staff, a Friday night theatre trip. An hour after leaving school on a coach, the students feel the call of nature. But the toilet door is locked and the driver won't open it. It turns out that the school has refused to pay for the "facilities".
Callum sighs: "That's a little bit soul-destroying, isn't it?" Sophie is less reserved. She kicks in the toilet door, but discovers that it won't flush because that's extra, too.
Another hour and we hit traffic. Sophie is increasingly vocal about her hunger. It was suggested that we could "possibly" go to McDonald's, but now we're stuck in a jam with the curtain call approaching. Sophie does not deal in the word "possibly". For her, the Golden Arches held more appeal than the theatre: "I don't see why you'd fucking say something like that if that ain't what you're gonna do."
Me: "Please don't swear."
Sophie: "Don't you start having a fucking go at me. It's not my fault this shitty school can't keep its promises. Plus, I've got medical conditions and if I don't eat soon I'm gonna faint."
Me: "Really? How long will that take?"
Sophie: "Oh, that's charming, that is. I wanna get off this fucking bus now!"
Me: "If I could let you off, I would. But we're on a motorway."
The journey is interminable. The students sitting opposite me are snorting Tabasco. Yes, Tabasco. They are challenging each other to ever bigger lines and dribbling red snot down the chair arms.
Finally, we have to concede that we've missed the play. Worse, without negotiating a labyrinth of red tape we are unable to replace it with anything else. Well, almost anything else. We pull into McDonald's and, under the light of the arches, no one utters a word.
Very few restaurants can handle this kind of onslaught. There are small incidents involving airborne McFlurries and a toilet smoke alarm, but the friendly manager is unfazed. Sophie asks him if she can take him home to be her grandad.
The journey back is dominated by the stench of McDonald's-fuelled effluent coming from the loo. Students clamber on to each other's laps to escape and, in an act of dejected nobility, staff take the seats near the toilet. The driver moans that we aren't doing our jobs. This may be true but it makes the students like us more. Now it is "us" versus the "evil driver".
When our ETA hits midnight we have to call 75 sets of parents to rearrange pick-up times. Astrid, a poetic type, says: "So, let me get this straight. We drove to London, missed the show, bought a burger, drove back and now we're going to be even later than if we'd seen the show?"
But along the way we've realised that we kind of like each other, which is probably the whole point. Theatre be damned, most of the time young people are theatre enough.
Nelson Thornberry is a pseudonym. Read his blog at disgruntledteacher.tumblr.com. He has been shortlisted for a TES writing competition. Vote for a winner at tesconnect.comcolumnistcomp