I had a thoroughly pleasant weekend, but it was overshadowed by a depressing incident on the Northern Line this afternoon.

Jenny and I were travelling south at about 1pm from Highgate, sitting in the rear section of the last carriage. There were a couple of girls sitting a few seats away who were clearly bound for Camden Market, because they had their noses pierced, and Camden Market is a fantastic place to walk along at 0.03mph if you've got your nose pierced. Just after Tufnell Park a black guy, late 20s, in regulation hooded tracksuit, walked down the carriage towards us and stood opposite me. He thrust into my face a copy of Friday's Evening Standard, on which he had scrawled in red pen:

MY NAME IS MARK. I NEED TWO POUNDS. I WILL PAY YOU BACK.

He held my gaze over the top of the paper. I looked back at him. He looked back at me. I could tell that he really wanted this £2 rather badly. But although I do give money occasionally to strangers who ask (depending where I am in my biorhythmic cycle) I don't appreciate being intimidated into giving, which is why I never succumb to the lunchtime charity-ambush on Camden High Street.

“Sorry mate, I don't have any change.”
He stood there, jabbing his finger into the front of the newspaper.
“Yep, sorry, I don't have any.”
This wasn't the answer he was looking for. “How much have you got?”

“Sorry?”
“How Much Have You Got.”

I don't know what it was about my demeanour that made him think that I was lying. He wasn't coming across as a particularly sensitive reader of human emotions. But, as it happened, I was lying. The Camden girls were visibly shrinking into their seats, while this guy pressed me on the quantity of change I might have in my pocket.

“I said, I don't have any-”
“CAN'T YOU F*CKING READ? IT SAYS THAT I WILL PAY YOU BACK. HOW MUCH HAVE YOU GOT.”

What do you do? This guy wasn't going to go away. He looked mean. Really mean. I was scared. I held out as long as I could, looking at him, and then reached for my pocket and scooped out whatever was in there. I looked at the coins in my hand: 78p.

“There you go. 78p. That's all I've got.”
“Right, now you give me your phone number.”
“Er, what?”
“SO I CAN PAY YOU BACK.”
“I tell you what, why don't you just keep it. Have it.”

He walked away down the carriage. Jenny blew out a long breath of relief. But he was coming back. He sauntered past, and towards the Camden girls.

“You got a cigarette?”

“Yes.”
“Can I buy one off you? I've got the money, here.”

They silently exchanged a Marlboro Light for 50p – my 50p – and he walked off, into the next carriage. I sat there, fuming, thinking of all the things I wish I had said, but how I knew that actually – for my own safety – I'd probably played it exactly right. When we got off at Old Street, he was still sitting on the train, and I felt I had to do something. I legged it upstairs, and collared a chap in an LU uniform. Breathlessly I told him that there was a guy demanding money with menaces on the train that had just left, going southbound. He nodded. “Yeah, a really unpleasant bloke, wouldn't leave me alone. I, er, he took, er, 78p.” The guy raised his eyebrows. I was complaining – with a slight hysteria due to a dash up an escalator – about a man who, without a knife or indeed any weaponry, had relieved me of 78p. LU clearly have bigger fish to fry. He nodded again, and walked a few yards away, doing nothing about it. So, that's that then.

As I say, depressing.