Just answered the door to a MORI poll lady. She’s doing a survey of young people in Highgate.

‘You look like a young person,’ she says, getting out her clipboard. ‘How old are you?’

‘Thirty-six next month.’

‘Good lord. Sorry for waking you’.

It’s half-past one in the afternoon. She moves on down the road. Though not, sadly, as Diana Ross did in The Wiz.

Naturally, I can only find it cheering to be genuinely mistaken for a twenty-something. Though I have friends of the same age who are still asked in a pub to prove they’re 18.

There’s plenty of others in this condition of blessed youthfulness, or indeed arrested development. Particularly those I’ve known for over ten years on the London music scene. Some of it is down to dressing like a younger person, with a younger person’s hairdo. If they do have jobs, such jobs often endorse and encourage a clinging to one’s youth: the music business, popular media, fashion, new technology, gadgets.

One place which encourages a more pernicious regression, if not downright schizophrenia, is the interactive side of the Internet. I’ve seen the anonymity of blogs and message boards turning perfectly intelligent and thoughtful graduates into the worst aspect of their childhood selves. Or perhaps they’re created new childhood selves, making up for some past wrongs. Victims of bullying in the real playground becoming virtual bullies online. An explanation, but not an excuse.

Such adults go out of their way to don a virtual mask – and a virtual school uniform if not a nappy – and adopt one or more of the time-honoured playground roles:

1) the spiteful, foul-mouthed bully
2) the whining victim telling tales
3) the self-appointed joker playing to some imagined gallery.

But meet such people in person, away from their devil machines, and they seem entirely reasonable and sane adults, who believe in love and hope and responsibility for one’s actions. And then they go back home, log on, and out comes the problem child all over again.

If I have ever inadvertently joined in with this Net equivalent of Knock Down Ginger myself (being the childhood ‘game’ of knocking on a front door, then running away giggling), then it’s always with my own name attached, striving for accountability. I feel the need to be found standing sheepishly in the doorway afterwards, facing the music. By myself. With a name tag. Any hoped-for giggling rings hollow and nervous and sad. It’s been a waste of time.

The trick is to write as if absolutely everyone in the world was right next to you, in the room, reading over your shoulder. And at the front of the crowd is the person you’re writing about at the time. Then if you are still childishly unkind, at least the schizophrenia aspect can be reigned in.

I’ve only been on ‘Second Life’ once. Within minutes of arriving in this animated virtual playground, one of the other newcomers (male) attacked another (female), knocking her about and calling her names. Just because he could. It was a kind of Second Life Rape.

I think of all that adult ingenuity, creating computers and computer programs, designing new types of silicon chips and so on, only to enable other adults to don child masks and regress in all the cruelest, most depressing, hollow ways. Not to add and improve, but to subtract, dilute, delete and undo. The worst side of the vandalism instinct, gorged with the playground mentality.

Some vandals can indeed be creative, such as Banksy (I do wince at his Grange Hill-like name) the graffiti artist turned darling of the coffee table books. But he works on his own. His defiling of Paris Hilton CDs wasn’t his greatest moment: it was cheap and obvious, and a bit of a childish regression on his own terms. Playing to the most tiresome kind of gallery. But at least he put his name to it. If not his face, of course.

When there’s a gang or a gathering, the bigger the numbers, the more chance of someone defining themselves by playing up to their worst aspect. I’m mindful of the ‘graffiti bomb’ of Camden Town Tube last Christmas Day.

On this, the only day the station could be closed, a group of spray can guerillas broke in and covered the walls with various daubings, in-joke images, ‘tags’ and taunting messages to the police, with whom they were playing a catch-me-if-you-can party game. What’s wrong with Naked Twister, I say, but anyway.

Some of it was rather jolly: a big silver ‘Merry Xmas’ all along one platform wall, beautifully outlined in that chunky letters way (though I’ve never understood why the 2007 graffiti style hasn’t changed from early 80s New York subway art one iota. Apart from Banksy’s style).

Others in the gang were less clever: a poster for a Downs Syndrome charity amended with the words, ‘Kick his face.’ So much for the romantic rebel. Even criminal gangs need their own moderators.

If I’d been in that gang, I would have scrawled, ‘Damn it. I’ve missed Doctor Who. AND these fumes are giving me a terrible headache. Frankly, I’m beginning to question if this has been the best use of my time.’