Leave your hat on

The first rule of Hat Club, is don't talk about Hat Club. So say the huge banners hanging in SeOne, the cavernous venue beneath London Bridge station, when we arrive at 1am on a Saturday. Joint first rule, as you might guess for clubland's most colourful, fun and outrageous headwear party, is that it's compulsory to wear a hat for entry.

Not sure of what to expect on our first visit, my friend Jaime and I opt for alternate ends of the hat spectrum. So while I take the root of tradition and don a felt porkpie hat, she elects for the more experimental choice of a knitted doily. We are both surprised at how donning headgear for a night out makes us feel instantly jaunty and just a little bit silly.

The entrance to SeOne lies in the tunnel of Weston Street, providing a refuge from the elements if you're waiting for a cab home, or grabbing a cigarette in the smoking area outside. When we arrive at 1am, we've missed the queues so, with a nod from the hat inspector on the door, we pay our £15 entry money and we're quickly inside.

After visiting SeOne's cloakroom, itself bigger than many clubs, we walk directly into the vast main room where we're greeted by a sea of hats and pumping, funky house music. With the party already in full swing, we can just about make out a stage where the DJ is at the end of the room, a huge crowd filling the dancefloor and a raised podium along one side.

With a round of sambucas (at £3.50 each) dispelling any residual self-consciousness about our hats, we hop up to an elevated seating area to get a better view of the scene in front of us. From beanies to berets, straw hats to stetsons, panamas to pillboxes — every size and shape of hat imaginable bobs about in front of us. There's even a foam Guinness hat — the sort worn by everybody except the Irish on St Patrick's Day.

Making our way on to the dancefloor, we find many of tonight's crowd — a mix of twenty- and thirtysomethings — have gone the extra mile with their look. Dancing with a group out celebrating their friend Gemma's 21st birthday, we feel distinctly under-dressed, as many of the girls are in full outfits. It's like getting down with the female equivalent of the Village People, as we boogie alongside a cowgirl, a policewoman and an Army cadet, while DJ Sonny Wharton spins chunky, energetic house

As the drinks flow, much hatswapping follows. There's such a friendly atmosphere and everyone is giving everyone else the eye, complimenting each other's headgear and having a go with other people's hats. The porkpie makes way for a black-spotted shower cap topped with pink bow, and then a Mr Ben-style bowler. The doily is exchanged first for a lollipop lady's school-crossing hat (allegedly found, not stolen), then the kind of deerstalker so loved by Johnny Borrell and indie kids in Shoreditch.

It's a great way to flirt and break the ice and to engage people in conversation — we both swap numbers with a few hotties.

We make our way around the stage to the smaller second room, red lighting and leather sofas around the walls giving it a more intimate feel. With DJs Catz (both in hatz) spinning a deeper house sound we meet Dan Evans, one of four friends who started Hat Club in a small bar in King's Cross two and a half years ago.

Originally conceived as a way of dressing up without really dressing up, the club has taken care to maintain its original core crowd — clubbers dedicated to the spirit of fun. And as well as regular bi-monthly events in both Brighton and London, Hat Club has taken its heady entertainment as far afield as Germany, Ibiza and Dubai.