The Libertines, Forum, London

Carl Barat and Pete Doherty put past differences behind them to remind us why the Libertines were such a cultural phenomenon

My first sound and sight, upon stepping out of the Tube into the pissing-down pavements of Kentish Town, are a wailing siren and a flashing blue light.

Oh no, not again Peter, surely? But the fluorescent jam sandwich speeds on past the Forum and away towards Hampstead. If anyone's going to stop Barat and Doherty this time around, it will only be themselves.

Before the Libertines' comeback has even begun, the celebrity circus that's sprung up around their personnel is already in full swing. Halfway up the open iron staircase on the left of the auditorium stands a beehived Amy Winehouse, regally holding court with bouncers in tow, receiving booze and boos from the plebeians down below, and eventually, when annoyance at her attempt to steal the show has reached critical mass, a chorus of "Who are ya? Who are ya?". Winehouse wasn't here in 2004, that's for sure. Mind you, in 2004 the who-are-yas would have been genuine.

On the face of it, the hysteria surrounding the cultural phenomenon of the Libertines – a passably good indie rock band whose Jam/Clash/ Smiths xeroxes were always somewhat on the slight side, but no more – was baffling. But cultural phenomenon they were, at least to a certain subset of a certain generation, among whom broke out a very old-fashioned kind of fandemonium that most assumed had died out.

The mania can be explained by three factors. First, the sex. The Libertines' twin frontmen were an odd couple. One, a classically handsome pin-up, the other a whelpish urchin who was a dead ringer for the young Rodney Bewes circa Billy Liar, but somehow had that star stuff, the unquantifiable qualities that get their hooks under your skin. Together, two skinny boys in too-big guardsmen's jackets singing into each other's faces close enough to kiss, or colliding like pool balls, was pure homoerotic catnip.

Second, the spontaneity. With their guerrilla gigging, their propensity to invite scores of fans into their living room for an ad-hoc happening and to give new songs away online, they temporarily broke the tyranny of the music industry's model of single-promo-album-tour. (It didn't last long.) And, ironically, their spontaneity unleashed a Silurian slurry of regressive imitators, public school berks in pork pie hats playing featherlight busker-rock and skiffle-ska (an era which has, mercifully, passed).

Third, the story. The Libertines, more than most, understand the power of myth, and the value of romanticising yourself as you go along (rather than waiting for others to do it for you in retrospect). I have it on good authority that, when Doherty was first kicked out of the band, Barat would receive condolences with a smile and a reply of "Oh, don't worry, it's good for the press." What happened next was a textbook case of "be careful what you wish for", as P-Doh turned into last decade's red-top bad boy of rock 'n'roll (albeit most readers couldn't name a song by him), the gutter press slavishly recounting his every antic, whether breaking into his bandmate's flat, beating up a film-maker, pursuing an on-again-off-again romance with a supermodel, stumbling in and out of Pentonville on drug offences. He even became a national hate figure for cruelty to cats long before we'd heard of Mary Bale.

It's moot whether this is their first comeback show or their 18th. Since 2004, throughout the Libs' hiatus and the lifespans of the mostly abysmal Babyshambles and mostly workmanlike Dirty Pretty Things, it seems barely a month has gone by without Pete 'n' Carl getting back together, whether on a pub sofa in Camden, or the stage of some dive in the enervated east or wasted west of London at a "secret" show that always mysteriously had an NME reporter and photographer present for a news spread. And even this Reading-Leeds warm-up isn't strictly their reunion debut: they played a closed-doors rehearsal show here to 500 friends the previous night.

Regardless, the mania is ratcheted up via Vera Lynn's "We'll Meet Again" and a slideshow of classic Libs photos, and the very theatrical hoisting of their The Libertines backcloth behind Gary Powell's drum kit receives a louder cheer than anything most bands I write about in this column actually do with their instruments.

When they finally saunter on in tight sweaters and V-neck Ts, flouting the cigarette ban, and rattle into "Horrorshow", beer flies in the air with the joy, abandon and lack of consideration of bullets at an Arab wedding. In an instant, my suspicion that the Libs left it too long and no one cares any more is looking a little silly.

After which it all becomes, well, professional. Carl's been making noises in the media about the music being right, and for the first time in their lives, they've nervously erred on the side of caution. There's precious little in the way of drama, aggro or chatter. Even the buddy act is toned town until "Can't Stand Me Now", their open-veined break-up song, is delivered to each other, and "Music When the Lights Go Out" is sung nose to nose.

The main set closes with their finest moment, "Time for Heroes", and comically, right on that wonderful line "there are few more distressing sights than that of an Englishman in a baseball cap", their merch guy, wearing one, vaults over the counter and runs out, as if shamed into quitting on the spot.

A nine-song encore, including the Libertines' other truly great moment "What a Waster", ends with a stage-managed hug, and a Doherty declaration that "Ladies and gentlemen, we are the Libertines." Yes, they are. And this time, they owe us more than one and a half semi-decent albums to justify the fuss. We'll be waiting.

Next Week:

Simon Price dries out his thigh-high waders after the Reading Festival