The mission Sit in silence, avoid eye contact, goes the London Underground etiquette. Chatty Mathew Sweet is having none of it

Talking on the Tube is a cardinal

sin, like kicking a vicar. It's just not

done. Etiquette demands that you hang on to your strap like something in an abattoir. Unless, of course, you're on a mission to get people talking.

I hop on the Circle line at Embankment. It's a clammy August day, and my carriage is full of men in nylon shirts with arrowheads of sweat pointing towards their bums. When your face is being pressed hard against some suitboy's ripe armpit, it's difficult to breathe properly, never mind dispense bon mots. "Hot in here, isn't it?" I venture. Everyone assumes that I'm talking to somebody else, so I home in on the man next to me. "Now you know how a lobster feels." He's not playing.

We reach Victoria, and the doors slide open. "Passengers are reminded that there's plenty of room in the rear carriages ... and on the roof." A godsend. A witty remark from the station announcer. A talking point at last. The man with the armpit is still standing next to me. "Did you hear that?" I breeze, giving him a verbal nudge in the ribs.

"What?"

"He said there's room on the roof."

"He can't have done."

"He did."

"Well, why don't you go and sit there, mate?"

He shuffles off at Paddington, where I'm able to nip into a seat. I'm now placed next to an impossibly ancient old lady. In my experience, old people need only the smallest encouragement to ramble on about their personal experiences.

"Bet you've seen some changes, then."

"Yes, dear, I get off here." And she's off at Edgware Road, moving quicker than an octogenarian probably should. So I turn to the woman on the other side of me. She looks like a tourist, and is therefore probably less likely to think I'm a patient on day-release or a psychopath out scouting for victims. "Are you on holiday then?"

She looks round nervously, with an expression that suggests she thinks I'm about to go for her neck. "Yes," she responds, nodding. Bingo! And she can't speak English very well, which in these circumstances makes for a better conversation. In a quarter of an hour I have shoehorned the following information out of her: she's from Germany, she admires Princess Diana and she's going to the Tower of London. "If she'd lived I suspect that's where she would have ended up," I joke, unwisely moving beyond the comprehension level of Unit Six: At the Railway Station. She leaves at Tower Hill.

Moments later, a Sikh man asks me if he's going the right way for Embankment. That's right. Asks me. So this is how it ends. An hour of rebuffal, someone starts making conversation with me unprompted. My new friend has been over here from Toronto for a wedding. A big family occasion. A whole gang of relations travelled from Canada. "Seeing them next to my relations who've settled in England, they seem so Canadian," he remarks, and I'm suddenly struck by an image of all these people in turbans and dungarees, doing a hoe-down in an Essex churchyard. I would have liked to have gone. "A great pleasure to meet you," he enthuses at Embankment, warmly shaking my hand and clambering from the carriage with his suitcase. The doors slide shut. I look around at my fellow passengers, who are all poring over Captain Corelli's Mandolin, the London Evening Standard or one of those idiotic adverts for car insurance (the one where the man explains to his dog that his girlfriend left him because they fell out over which policy to choose). And I'm feeling rather superior to them. I want to tell them that they should put down their books and learn to talk to each other. But I don't, or course. And for the rest of the journey, the carriage remains as silent as a Buddhist meditation centre on the Isle of Arran