What constitutes a professional hairstyle? Is straightened hair any more or less professional than hair that's in its natural, curly state? Are braids more professional than china bumps? What about dreadlocks, or an afro? Does it even matter any more?

Well, apparently, it does. I've just had a call from a lawyer friend who's recently changed firms, saying she's been taken to one side and asked - politely, of course - if she could come back into the office on Monday with her hair "properly done". The friend was wearing her hair in cane rows, a style that takes at least an hour to do.

The sad thing is that, after my initial outrage, I realised I wasn't actually that surprised - and neither were any of the black friends I mentioned it to. Angry and frustrated on her behalf, yes, but not as shocked as you'd hope in the circumstances.

We may have come a long way from the idea that if you want to have a hope of working in an office, you had to wear your hair straight (or, at a push, tied back), but, judging by my friend's experience, not far enough. I don't know a single black man, for example, who works in an office and doesn't have his hair shaved in a close crop, and I don't know any black women working in the City who don't have their hair straightened. When I talk to these friends about it, male and female, their responses are virtually identical - "I don't want to look too black," says one. "I don't want to freak people out," says another.

"As much as it shouldn't matter, I think it does, especially for men," says my friend Nana, echoing the others."They wouldn't even let you through the door of some places in the City if you were a guy with cane rows."

As far as I can make out, the more traditional the style, the less well it is regarded. Whereas with white folk it's the other way around: it's the new Hoxton fins that are regarded with suspicion, rather than, say, the traditional short back and sides.