The Dublin Castle pub in Camden helped launch the likes of Madness and Blur. But of the hundreds of bands who; play there each year, most will sink without trace. So why do they do it? Well, you never know your luck, say one week's hopefuls
madness played there in the early days. Blur did a secret gig there recently. Situated right in the heart of the current Britpop scene (ie Camden, London), pub venue the Dublin Castle plays host to roughly 20 bands a week - some on their way up, some on that middle level endlessly flogging the London "chitlin' circuit", and some who have already been up and are now on their way down. Most of the bands, though, are new outfits who are intent on making it. So are they all pimply 17-year-olds with stars in their eyes, desperate to be the next U2? I spent a gruelling week at the Dublin Castle to find out.

TONIGHT it's Club Spangle, rapidly establishing itself alongside the Splash Club in King's Cross as the hottest night for hip indie bands. I meet the headlining band scheer in the local pizzeria. They have the relative luxury or a meal beforehand and a place to stay (albeit on the floor of their record company offices) because they've recently been signed to 4AD, label for the Cocteau Twins and leading US guitar bands like The Breeders and The Throwing Muses.

"It's better than sleeping in the van, which is what we used to do," says bassist Peter, covering his pizza with tomato ketchup. Hailing from Co Derry, Northern Ireland, the band left Dublin at 9.30 the previous morning, arrived in London 12 hours later, and intend to stay for a week doing promotion.

Peter, scarlet-haired singer Audrey and Niall, the guitarist, met at the University of Ulster and soon after graduation they teamed up with Joe and Paddy, friends from the local band scene. That was three years ago and they are well known in Ireland, but here they have to start again, from the bottom up. "We'll be playing all the toilets and Dogs & Ducks in England for a while now," says Audrey philosophically. Despite a steadfastly unreconstructed appearance, this lot take their rock 'n' roll seriously - there's no question of day jobs, this is their job.

Half an hour later scheer are on stage. The conditions are basic and the schedule is strict - you're up and you're on, even if it means playing to three men and a dog. Tonight, though, the place is full, the atmosphere expectant. There is a sense of brisk dedication about this band. From the opening deep thrash of guitar chords, their sound is hot, heavy, metallic and melodic, a cross between grunge and dark Gael-force folk. As one Melody Maker journo has already said, they will probably headline Reading next year.

"THIS IS a permanent, raging full-on thing," says Mark Hoyle, vocalist with Dumb. "The only thing that gets in the way is working to pay to do it. We think about it every waking moment."

Mark finances his music through youth work on Moss Side. He formed Dumb just over a year ago with bassist Cathy, who has a PhD in immunology and a job as an environmental officer. Friends joined to make it a tight- knit unit, with Jay, a former Kung Fu instructor on guitar, his sister Beth, an ex-dancer, playing percussion and Jonny, who gave up 12 years of upholstering to do a sociology degree and drum.

Tonight's headliners, Dumb are signed to Thrill City Records, a tiny underground label based in Manchester, to whom tonight's bill is dedicated. After the gig they'll drive their hired van back to Manchester at 1am, arrive home by 6am, then go to work. "We choose gigs pretty carefully, we're not in the market to play a week of shit-holes to four people. We prefer playing Manchester but we have to come down here because the press never leave Camden, let alone London," says Jay. The five-piece might just break even after the regulation 20 tickets are sold, but they reckon the lousy money and all the travelling are worth those 35 minutes on stage. When they launch into their angular, cutting pop noise it is as if they have been preparing the whole day for this spitfire moment. It's refreshing to see the two women in the band playing serious instrumentation rather than acting as vocal decoration. And as a nice touch their drummer Jonny plays hardcore beats in a suit and tie.

These sparks of originality, though, are lost on the crowd. A man in an Eric Clapton T-shirt has paid pounds 3.50 to shout to anyone who'll listen: 'Call this f-----g rock n' roll? This is f-----g bollocks!' Ah, another day in the life.

IT'S A completely different crowd tonight, more thirtysomething, more laid back. Tuesday is the charmingly named Club Zitt, the theme a kind of burnished post-apocalyptic pop cabaret. Headliner Terry Edwards, an affable chap who used to be in the early Eighties Norwich band The Higsons, plays a wild sax with his band The Scapegoats, whilst The Unsophisticates do intolerably intense things with drumsticks.

It's the "middle" band I'm interested in, a four piece called Gretschen Hofner. We sit in the "dressing room", a tiny, cramped back room with rain dripping through the ceiling and, somewhat inexplicably, a large unused Aga stove shoved against the wall. Describing themselves as "an arthouse distillation of the Velvet Underground and Come Dancing," the band are beautifully turned out - suits, silk shirts, sequins, shiny shoes. Having met through the buzzing community of Gibson Gardens, N16, a creative enclave not unlike Bonnington Square in Vauxhall, they now have a small record deal and finance the band with haphazard day jobs. Geoff, the drummer, used to be a psychiatric social worker and now services pinball machines because "the hours are flexible". Vocalist Paul writes freelance for technological titles, while pianist Justine gives music lessons and bassist Kieran is a studio engineer. Average age 32, they are too old to be seduced by mega- stardom, and will happily settle for cult credibility like heroes Captain Beefheart and The Cramps.

"At the end of a gig strange, sallow people with slightly bug eyes come up to you. They love you, but it's a bit creepy. And we get odd letters from Israel, Romania, New York. We inspire a sort of fanaticism. I like it," says Paul, proudly.

TONIGHT the A&R posse are out in force to see the opening act Wonderland, a new unsigned band from Oxford, home of chart heroes Supergrass. Unfortunately, when Wonderland come on at 9.30pm, the lights fuse, and they perform in candlelight. Despite being compromised by the light and the mix, this band have everything - youth, sex, and attitude. Not only do they sound like a compulsive pop crossover between The Cranberries and Dinosaur Jr, the lead singer resembles a baby Debbie Harry and the bassist looks like Brad Pitt.

Outside on the pavement Wonderland are feeling anti-climactic. "It was shit," says vocalist Leigh. Having been together for less than a year, this is the band's first London gig. "We knew A&R people were here, that was why it was important to sound really good." All in their early 20s and on the dole, they got together through Oxford rave parties organised by bassist Joal and guitarist Matt, "We'd project Alice in Wonderland up on the wall and put the film through digital delay pedals and wah wahs," says Joal.

When they grew tired of that they formed a band with Rich, another guitarist, and Leigh. Stuart, the drummer, they found one day banging water cartons on Glastonbury Tor. Leigh, it seems though, is the main songwriter and guiding force. Her father was in a Sixties pop band called The Sorrows who toured Europe and made an album called Pink Purple Yellow & Red. Her aims are simple. "Superstardom. To be as big as U2, We want to own TV stations, record companies and do our own A&R-ing." Attagirl.

IT'S PUNK night, and the place is filled with spikey hair, leather jackets and war paint. It could be 1977 but for the fact that most of the crowd are French or Yugoslavian. Pedja, for instance, dressed in leather with perfectly coiffured black tufts, comes from Belgrade. At 20 he is too young to remember the "first wave", but he loves the music, "It's rare to get a night like this in London," he says.

Punk stalwarts UK Subs are headlining, while London trio The Stains provide support. Having just signed a deal with Dough Joe, a label that also has The Selecter and Bad Manners, The Stains have their eye on success in the States. "Punk's in vogue there," says John, the bald-headed bassist. "It's also big in Europe. England's the only place you struggle - here it's all trendy pop bollocks."

Describing themselves as "old codgers", they are in their early 30s and remember punk in the good ole days. Having been in various band permutations for years, this is the first time it has gelled. Even though they are fans of everyone from Slaughter and the Dogs to "classic Pistols", they insist that theirs is not a nostalgia trip - "If it was nostalgia we'd get up and do a load of old bloody covers," says Simon, a van courier. "What we do is relevant," chips in drummer Gary (Baldi), a drainage surveyor by day. "We sing about the music media, have a bash at them 'cos we hate them. We also sing about one-sided love affairs, joy riders."

Later I see them on stage, guitars slung low Sid Vicious style, clattering drums. I could be in a time warp. Time to drink up and leave.