Scotland’s biggest music festival turned 15 at the weekend, as 85,000 people filled a disused airfield between Edinburgh and Perth and made it the country’s fifth largest town for three days.

Defying gloomy forecasts, T in the Park basked in a sustained stretch of blazing sunshine before the rain fell late on Saturday night, turning the Balado site into a mudbath.

Once notorious as a beery, rather belligerent cousin to other British festivals, T in the Park has improved its image in recent years, introducing genteel innovations such as fancy dress and a healthy food village. But it still has a distinctly Scottish flavour, from backstage bagpipe bands to food stalls offering tatties, neeps and stovies.

But the atmosphere was still unmistakeably booze-soaked, and peppered with the kind of weapons-grade swearing rarely heard outside of an Irvine Welsh novel. This year’s line-up was arguably the best to date, a greatest hits mix of Glastonbury and Latitude including Blur, the Pet Shop Boys, Elbow, the Specials and the Kings of Leon.

While some English festivals have begun to resemble a musical Antiques Roadshow, T in the Park has swung the balance back towards a younger, poppier event with more female-centric acts. Lily Allen, Little Boots and the Ting Tings all played, though Lady Gaga stole the show with her flesh-baring, costume-changing, scooter-riding extravaganza. Her biggest hit, Poker Face, was transformed from an anaemic chart plodder into a celebratory mass singalong.

Lady Gaga, of course, is essentially rehashing Madonna’s soft-porn, disco-trash peak. But she does it with an audacious swagger and may well, I suspect, turn out to be Sacha Baron Cohen’s most beguiling disguise yet.

T in the Park may have belonged to the younger stars, but some of rock’s elder statesmen also played thrilling sets. The Manic Street Preachers, returning to Balado for the first time in a decade, were greeted like conquering heroes. Nick Cave and his Bad Seeds were also on tremendous form, gnashing and roaring like snaggle-toothed, scurvy-ridden pirates steering a hijacked galleon through a howling gale.

On Cave classics such as Deanna and Stagger Lee, the lanky Australian singer turned into a kind of skeletal Tom Jones, grinding his stick-insect hips in a grotesque parody of a Dionysian sex god. Literate and louche, these desperate romantics were far more of a rock’n’roll spectacle than any of the weekend’s youthful acts.

In longstanding festival tradition, a rapturous reception awaited the homegrown talents, from the obscure jazz-punks Punch and the Apostles, to the mega-selling coffee table troubadour Paolo Nutini. Franz Ferdinand also played a muscular set of square-jawed, lumberjack-shirted funk-rock, getting the entire crowd bouncing to Take Me Out before closing with an extended blast of New Order-ish electro-pop. Very nice.

Their fellow Scots, Glasvegas, caused a near-riot when fans stormed the fences around the overstuffed King Tut’s tent to roar along to their heart-swollen, flag-waving terrace anthems. After opening with the supercharged version of the bittersweet social-realist epic Geraldine, James Allan bellowed “Scotland, I f***ing love you!”, stating the painfully obvious as he cranked out all the wounded pride of Clydeside at ribcage-crushing volume.

To judge by the hordes of sweat-soaked fans stumbling from the tent, dazed yet elated, the feeling was clearly mutual. Even non-Scots were keen to ingratiate themselves with the locals, not always convincingly. The tiresomely perky Californian pop princess Katy Perry wore a tartan mini-dress and rechristened herself the Loch Ness Monster — a tactic that felt shrill and calculated, much like her songs. Florence Welch, the Londoner who fronts Florence and the Machine, even wrapped her pre-Raphaelite copper tresses in a Scottish flag. It was shameless, but effective.

Headlining the main stage, Brandon Flowers, the Killers’ lead singer, punctuated his shiny shopping-mall tunes with references to haggis and the infamous low-rent booze, Buckfast. It was a characteristically careerist move from the Tom Cruise of slick-yet-addictive stadium pop, but the crowd at T in the Park lapped it up anyway, giving the Las Vegas visitors a typically rowdy, big-hearted send-off.

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