In my week: We are talking about serendipity... on the two occasions in my life when I have reached absolute desperation I have found a pounds 50 note on a busy street

We're playing pinochle. I am winning by about a million points, but tragically I'm the one who vetoed playing for cash, and it'll be a bit obvious if I change my mind now, so I have to settle for the simple pleasure of humiliating my companions. The coffee table is crowded with the usual mass of empty wine bottles, full ashtrays, lumps of driftwood and bank statements on which Dan, who is 19, has doodled so many marijuana leaves that the figures have been obliterated. Dan has gone out, looking insulted when asked conversationally where he was going. Dan and Charlie exist, I think, to remind me that, in some people's eyes at least, I am now a member of the older generation. I wish they'd tell that to the 70-year-olds. Charlie is lying on the sofa in the kitchen watching a Steven Segal film on cable.

While we slap cards down on the table-top, between cackles and cusses, we're talking about serendipity. It's been on my mind ever since I dropped the money. It was one of those things where you think you're being crafty and actually you're being amazingly stupid. I was going to Tooting. So naturally I assumed I was going to be mugged. The moment Londoners step outside areas they are familiar with, they prepare to enter bandit country. Never mind that your best chance of being robbed is to walk down Oxford Street: the mean streets of Surbiton are full of threats if you look for them.

In anticipation, I had transferred some cash into one of those silk purses with poppers which the Chinese wrap cheap jewellery in. This had the advantage of separating it from my credit cards, but it weighed nothing at all. Tooting was fine: not much street lighting and a lot of second-hand shops. At four in the morning, however, as I rolled from the back of a minicab, the stupid sow's ear dropped from my pocket, and pounds 40 drove off into the night.

The thing is, though, after an initial five minutes of kicking cupboard doors, I don't really mind. Someone poorer than me, if there is such a thing, will probably have found it. This is where the serendipity comes in. On the two occasions in my life when I have reached absolute desperation: rent due, contracts reneged on, no food, no fags, I have found a pounds 50 note in a busy street. What you do when you're miserable, of course, is look down, which increases your chances of finding what's on the pavement, but I have never, apart from these two incidents, even seen a pounds 50 note. They are things you buy second-hand cars with, not things that drop out of your wallet.

I finish telling this story, and Laura says "Ooh, that reminds me. Did I tell you about what happened to Dan and Charlie the other day?" Dan and Charlie have a bit of a reputation for spooky happenings. "No," we say. "Well," says Laura, and I don't notice that she's continuing to play while she talks, "Charlie went out a couple of nights ago. Went up to see some friend in Notting Hill. Of course, he hadn't said he was coming, so his friend was going out. They ended up in this house in Shepherd's Bush. Charlie had never been there before. Didn't know these people from Adam. Wouldn't have been able to find his way back to the Tube station. Anyway, they're all sitting around like they do, and the phone goes. For some reason, Charlie picks it up". "Mmm?". "Well, you won't believe this, but this voice goes "Hello, can I have an American Hot delivered?" And Charlie goes "Wrong number," and the voice goes "Charlie?" and Charlie goes "Dan?". Dan had dialled a wrong number trying to order a pizza from Clapham Junction.

"Whoo," I say. "Freaky." Laura pours herself another glass of wine. "By the way," she says. "You need to pick up two cards for missing your go." "It's John's turn." "No it isn't. I put down a Jack." "Oh you sod." I start losing and end up several hundred matchsticks down by the end of the evening.

The next night, I go to the home of my Scottish godchild, strapping on my knuckle-dusters to negotiate the obvious dangers of Tufnell Park. The house is in the grip of a bout of projectile vomiting; I time my journey to arrive just after bathtime. Since I last saw him, Hector has graduated from his cot. I get one of those life-is-passing- me-by flashes; it seems no time at all since people were exhorting me not to stick my fingers through the holes in his skull. He explains the entire plot of a dinosaur book and I retreat to the safety of the kitchen before he can tell it again.

Inevitably, we get back onto serendipity. I explain the rules of pinochle, then tell the story of Charlie and Dan and the pizza. We're calculating the odds of dialling a specific wrong number in a city of 10 million-odd people, combined with the odds of a run of luck at cards ending at a given point, when Hector comes into my mind. "When did Hector get a bed?" "Months ago," says Jo. "Don't you notice anything?" Jo and I shared the same bathroom facilities for three years, so she feels entitled to be familiar.

"I noticed you'd finally thrown away those three-year-old Review sections in your downstairs bog. How's he getting on? Has he fallen out yet?" "Amazingly enough, no. I keep expecting to hear a loud..."

Thump. Hector plunges to the floor above us just as the word crosses her lips.