Long hair is back, at least to judge by the male models sashaying down the catwalks of Paris and London recently in shows for Marc Jacobs, Lanvin and Tommy Hilfiger.

This could mean one of two things. Either the oft-mentioned but never taken very seriously grunge revival is finally upon us – or a cabal of agents have decided there's an untapped market in promoting hair products for men and told their clients likewise. "Have leonine mane, will nab Revlon contract" might be the motto.

The strange thing about long hair is that when it becomes fashionable it does so suddenly. In theory, this shouldn't happen. Long hair should follow on from a trend for collar-length hair, and so we should see it coming. That's what happened in the 1960s. Since then, long hair seems to appear out of nowhere. Suddenly there are loads of blokes with tresses and curls where a week earlier everyone had a buzzcut or one of those Joey Barton-does-George-Orwell hairdos that used to be known as an Eton crop.

How does this happen? I don't know, because when I had long hair it took a considerable time to grow. In fact I had to set aside three years between leaving college and finding gainful employment, and it was a 24/7 project. So how do male models manage it? Probably through use of the same follicular juju that enables them, overnight, to look like Robert Plant out of Led Zeppelin and not (as I did) Geddy Lee from Rush. (If you don't know what Geddy Lee looks like, google him. But keep the kids out of the room. They'll have nightmares.)

And don't think the return of long hair won't affect men's fashion, either. For a start, it'll kick hats into accessory limbo for another generation. Worn with long or even shoulder-length hair, flat caps and trilbies will suddenly look even dafter than they do already. Flowing hair suits flowing fashions, so expect a turn away from skinny jeans too. Ditto suits. Even the long-haired John Lennon looked rubbish in a whistle and his was made by Savile Row legend Tommy Nutter. If yours is from Topshop, you're toast.

Mind you, there is one upside to the trend for longer hair – it's a potential money-spinner. The government can't force you to cut it but they could tax it. It's happened before: in 1795 the Duty On Hair Powder Act meant anyone using the stuff had to visit a stamp office and pay a guinea for an annual certificate. The only exemptions were soldiers, clergymen with an income of less than £100 a year (no bishops, then) and members of the royal family. The Act wasn't repealed until 1869, by which point men had got the message and trimmed their locks – which is probably why everyone wore hats until 1964 and wigs for men haven't come back into fashion. Yet. n