The Balgger's Guide To: The Hay Festival

The Hay Festival kicks off on Thursday, and runs until 10 June. Now in its 25th year, Hay is to books what Glastonbury is to music: starting from humble origins, it has become the biggest festival of its kind. Anyone from Jimmy Carter to Nigella Lawson can be expected to turn up, as bigwigs from the worlds of literature, politics, and history descend on the Welsh borders to plug their books. As at Glasto, it usually rains.

Founded in 1988 by local man Peter Florence, the festival is now a literary mega-brand. Its name is exported to 15 other sites around the world, including the Maldives, Mexico, and India. Some say it has got a bit too big: Barclays Bank sponsors a venue called "The Wealth Tent". Others point out that Hay has always aimed high: the founding sponsor was The Sunday Times. The festival now attracts an estimated 100,000 visitors, while the town's population hovers at 1,900.

In 2005, the festival got so big it moved to a site outside the town. Since 2002, it had been sponsored by The Guardian, though they lost the crown in 2011, when they were outbid by The Daily Telegraph. Last year, The Independent sponsored a small rival festival in the town, "How the Light Gets In", which was more in keeping with the kitchen-table feel of the early days.

The format remains unchanged: people talk, others listen; some laugh, others sleep; some joke, others heckle; then everyone goes to the bar. Swanky parties are held in big houses. The hottest ticket is on Sunday night, when film-maker Revel Guest throws a bash sponsored by GQ and Range Rover at her beautiful riverside pile, Cabalva. After drinks on the terrace and dinner in a marquee, luminaries take to the dance floor. Philosopher A C Grayling is a nifty groover.

Hay was a book town long before the festival, thanks to Richard Booth, the self-proclaimed "King of Hay". Until recently, he lived in the semi-derelict castle at the top of the hill. He opened the town's first second-hand bookshop in 1961, with the aim of creating the largest antiquarian book centre in the world. There are currently about 30 bookshops in the town, though that's down from a high of about 40. The internet is partly to blame.

Van Morrison played a five-and-a-half hour gig in 1999. Throughout, he was heckled by the late Christopher Hitchens, who demanded he play "Cyprus Avenue", from the album Astral Weeks. Morrison said he would sing a request for anyone who could identify a certain quote. It was by Oscar Wilde – and Hitchens got it right.

Countless spats and feuds have played out at Hay, though there have been reconciliations too. The most significant came last year, when Paul Theroux and V S Naipaul finally kissed and made up after a 15-year stand-off. It started after Theroux, a travel writer, discovered a book he had given to Naipaul, inscribed "with love", was up for sale for £1,000. Theroux hit back by writing a damning memoir of their friendship. Then, Naipaul called Theroux's work "tourist books for the lower classes". The novelist Ian McEwen bravely brought them together in the Green Room.

The Poet Laureate, Carol Ann Duffy, has spoken at Hay every year since the start. Highlights this year include novelist Hilary Mantel, baritone Bryn Terfel, and ex-Catatonia singer Cerys Matthews.