It is, perhaps, the magical "anything goes" quality of festivals that makes them so appealing to us (otherwise very social norm-abiding) Brits. Although fancy dress is on the rise at many music festivals, nothing comes close to the surreal outfits witnessed at Bestival each year, where, nestled among the hills of the Isle of Wight, the festival has become famous for its creatively themed fancy-dress weekends.

Founded and curated by DJ Rob Da Bank and his illustrator wife, Josie, Bestival is now in its 11th year, and is one of the nation's best-loved music festivals (in recent years, it has twice been voted the best major festival in the UK). In 2004, the festival's inaugural year, Rob explains, "we thought 10, 20, maybe 50 people might come in fancy dress, and we'd do a little parade in the middle of the madness. But no, half the site – a few thousand people – had got all dressed up. And they weren't run-of-the-mill, throwaway outfits, either, they'd really made the effort."

Photographers Dan Smith and Kent Mathews are keen Bestival-goers who fell in love with the unique spirit of the festival, and decided that they wanted to document the outrageously eccentric outfits on show. "The dressing-up aspect became a bigger and more important part of the festival over time, and we felt it was a quintessentially British thing to do," Mathews remembers. "The creativity and the energy that people put into it is just fantastic; some spent the whole year preparing." Smith and Mathews set up a photography studio on site in 2009 and 2010, capturing the best "outer space"- and "fantasy"-themed outfits against a white backdrop to take the revellers out of their festival context. The results, says Rob Da Bank, "look like a fashion shoot. You wouldn't think these people were stepping back outside into a festival."

The transformative power of fancy dress lends itself well to the parallel universe of a festival – it takes us back to our childhood, to dressing up and playing at being someone else. "The eccentric nature of dressing up makes a better party," says Rob. "You get on a ferry to the Isle of Wight, so already you're stepping outside of your usual boundaries, and then, once you're dressed up, even your friends might not recognise you, so you can let your hair down and go completely nuts because no one really knows who you are. For me, that's the exciting thing – seeing people turn into other people over the weekend."

For Mathews, dressing up is about "being part of something. Many of the outfits are hilarious and designed to make people smile. It's an amazing experience wandering around on the Saturday, the big fancy-dress day, because everyone you meet is in the most outrageous outfits – you're talking to jellyfish and spacemen and a gingerbread man… it creates an alternative reality. Everyone understands that and enters into this reality, and it's fantastic escapism, to take on the persona of the character you're dressed as. And you're not being judged by any normal standards."

Smith and Mathews' striking portraits celebrating the creativity and passion of Bestival-goers can be found in The Art of Dressing Up, published by Bestival Media, and will be on display later this month in Camden, north London, ahead of the "desert island disco"-themed Bestival from 4 to 7 September.

Absurd Observations: A Portrait Study from Bestival Exploring "The Art of Dressing Up", Proud Camden, London NW1, Wednesday-10 August 2014