Cropedy: The calm before the folk-rock storm in the Oxfordshire village

As the Oxfordshire village of Cropredy braces itself for the 40th-anniversary Fairport Convention reunion

At 12.30pm, in the Red Lion, Cropredy, an elderly ginger cat settles down to sleep. Some of the patrons watch him as the afternoon moves lazily on, the time marked by a mote-filled strip of sunlight from the dining-room window that makes its inexorable way across the red-tiled floor. Pints of Hook Norton are poured and downed, and he dreamily flicks one ear. Plates leave the kitchen, groaning with roast beef, and later come back empty, the waiters deftly stepping over his twitching tail. Outside, in the churchyard, it starts to rain, and stops again. He wakes up, stretches, turns around on his cushion and goes back to sleep.

These sleepy rituals are being repeated all over the village. A pied wagtail hops across the cricket pitch. Two water lilies gently open in the pond outside the Brasenose Arms. Three girls bowl little purple apples to each other on the Vicarage Green, before moving out of the way of a tractor, and under the bridge, half-a-dozen narrow boats nudge each other along the canal. But if Ginger has a long memory, he must know by now that his afternoon peace is about to be irrevocably disturbed.

Early on Thursday morning, they will start to arrive. First, the walkers and cyclists will begin trundling across the cricket pitch, denting the immaculate wicket, unfurling their moth-eaten canvas and spearing tent pegs into leg slip. The smell of bacon will waft from the Brasenose's garden as the first cooked breakfast of many starts to sizzle. Before long, the Vicarage Green, the tumbling churchyard and the eccentrically named streets – Cream Pot Close, Cup and Saucer, The Plantation – will be crowded with lolling folk, and it will be fender-to-fender down on the canal.

Sooner or later, a band will strike up in the beer garden of the Red Lion, and the old moggy will be out on his flea-bitten ear. Once a year, regular as clockwork, this small village is filled to its rafters with folk fans, as Fairport's Cropredy Convention moves into town.

Ever since 1979, before even the ginger cat was a fixture, the folk legends Fairport Convention have been kings of the village. The band, which first convened in 1967, held its first "farewell concert" here 28 years ago this weekend. Since then, while musical tastes have altered unforgivably and global warming has parched the Cropredy grass, somewhere in a field in Oxfordshire, some things will never change. Fish gonna swim and birds gonna fly, and it's always gonna rain when Richard Thompson plays at the annual music festival, according to legend. Dave Swarbrick will get sick and get well again, and newspapers will publish his premature obituary (as the Telegraph did in 1999), but he will always turn up as a "surprise guest" on the last night.

Cropredy remains a tiny bubble of constancy in a turbulent world. The only change is that the children dashing about, with painted faces and water pistols, are the children of the children who came with their parents in 1979. "It's a very old-fashioned approach," says Dave Pegg, the Fairport bassist who organises the festival. "It's called 'music'."

Previous acts include Steeleye Span, 10cc, Richard Digance and Glenn Tilbrook. This year's line-up is as catholic as ever. Jools Holland's Big Band will line up with Wishbone Ash and The Strawbs, who, back in the Sixties, bequeathed Sandy Denny to Fairport Convention. Richard Thompson will headline on Friday night, guaranteeing that this year's rain-drenched June and July will go on into early August.

Those who cannot stand a dose of Thompson mud will have problems finding a proper roof over their heads in the surrounding area. The Brasenose Arms, which sells home-made jam and marmalade alongside the real ales on its well-polished bar, sold out its B&B space a year ago. Some smug festival-goers will have booked a room in the magnificent Whately Hall hotel in Banbury, or in the 17th-century Wroxton House, in nearby Wroxton St Mary. Even smugger veterans will have moored their canal boat alongside the festival site: spaces are at such a premium that they often end up mooring two abreast.

But among genuine Cropredians, camping one-upmanship is as much a festival sport here as nicking your neighbours' fire wood is at Glastonbury, or shouting "Bollocks!" all night at Reading. Hours are spent eyeing rivals' gear, and the Banbury Millets is deluged with campers desperate to get hold of this year's gadget.

In 2002, when the rain fell without remorse and rivulets of water dribbled into pristine wellies and diluted the cool-boxed gin-and-tonics (Richard Thompson played a blinder that year), Oxfordshire sold out of canvas gazebos. But the following year, as the temperature rose to something like the combined age of Procol Harum, technology was called in.

Glastonbury's low-tech strategies for coping with the heat, like dipping your hat in water or fanning yourself with a rolled-up copy of the NME, are beneath the Cropredy vets. Here, you can park your car (or camper van, or motorbike) next to your tent, and all manner of household conveniences have been adapted to plug into a dashboard cigarette-lighter. Fans are de rigueur – one man was spotted wearing a baseball cap with integral solar panel wired up to a small fan. The "porta-potty" is becoming standard. Anyone without a mini-fridge feels a fool.

In good weather, walks along the river Cherwell take you past swans and bulrushes, thatched cottages and enormous lavateras, near a small farm selling duck eggs and baby rabbits, and eventually on into Oxford. A shorter walk is to Banbury, along the four-and-a-half-mile towpath that reeks of fresh rain and wild garlic. There, take tea at the Three Pigeons (where the namesake birds are woven in thatch on the pub's roof), or find the fine lady upon her white horse (her statue has pride of place at Banbury Cross, and with one ear regally cocked towards Cropredy, she still has music wherever she goes).

The Banbury museum is full of the area's canal-based industrial history, and tells the story of the Battle of Cropredy Bridge. In brief, the Parliamentarians faced the Royalists across the bridge in 1664. The stand-off lasted several weeks, until half the Parliamentarian army deserted, presumably to sit in the Red Lion eating bread-and-butter pudding instead. Now, nothing more confrontational goes on there than pooh-sticks, and the odd scrabble for the last newspaper at the marigold-spotted Spar.

But what the Cropredy set are really here for – and the reason they tolerate the rain, the spiders and the boiling nights under canvas – is Fairport Convention, the band who invited Sandy Denny to sing to their electric guitar and drums in 1968, and single-handedly invented folk-rock. More specifically, they're here for "Meet on the Ledge", the last encore on Saturday night, and the swaying, candlelit sing-along that many admit is the high point of their year.

They begin to gather in front of the main stage at noon, folding chairs under their arms, folding tables in their knapsacks, folding Irish coffees tucked into stripy-trouser pockets. They set up flags and flashing lights to mark their places – it can get confusing finding your spot and your extended family of 126 when it's dark, and you're old, and you've drunk 15 pints of Tanglefoot in the beer marquee. Most settle in the same spot year after year. The colonies of Dutch, Americans and Germans who gather to the right of the sound-tower are now firm friends.

On the last night of the festival, as the sun sets over the fields, 15,000 lanterns flicker into life, and 15,000 rugs are pulled over laps. Dave Swarbrick might be wheeled on stage, wearing an oxygen mask and wheezing through the fast songs. "We love you, Swarb!", voices will shout, with a wobble of emotion for the faltering hero. Then, as the minutes creep towards midnight, the encore that's as predictable as Christmas and twice as sentimental: Thompson's "Meet on the Ledge". "Meet on the ledge, we're gonna meet on the ledge," the crowd sings. "When my time is up, I'm gonna see all my friends."

Pissed bikers gruffly link arms. There's the glint of a tankard, raised in tribute. "Meet on the ledge, we're gonna meet on the ledge," they roar, as the lanterns flicker and Thompson blows a thundery breeze through the beer marquee. "If you really mean it, it all comes round again. It all comes rooound, agaaain."

Traveller's guide

GETTING THERE

Banbury is served by Chiltern Railways trains from London Marylebone and Birmingham Snow Hill stations, and by Virgin Trains cross-country services from stations around the UK (National Rail Enquiries: 08457 484 950; www.nationalrail.co.uk). During the festival, there is a frequent bus service between Banbury station and Cropredy; returns cost £5.

If travelling by road, the best route to Banbury is on the M40 motorway between Birmingham and London, leaving at junction 11, which is signposted for Banbury. Car access during the festival will be limited to restrict the number of vehicles leaving the site. This is because the soil on the festival site is still soft after the River Cherwell broke its banks two weeks ago.

STAYING THERE

Tickets for the festival (9-11 August; www.fairportconvention.com) cost from £45 for a Saturday-only ticket to £75 for a three-day weekend ticket, plus up to £26 for a weekend camping ticket.

The Brasenose Arms, is in Station Road, Cropredy, Banbury, Oxfordshire (01295 750 244). Sadly, all accommodation for the festival was booked up last year.

Whately Hall Hotel, Banbury Cross, Banbury, Oxfordshire (01295 253 261; www.mercure.com) has doubles rooms costing £155 during the festival, including breakfast; otherwise doubles start at £110 including breakfast.

EATING & DRINKING THERE

The Red Lion, Red Lion Street, Cropredy, Oxfordshire (01295 750 224; www.redlioncropredy.co.uk).

MORE INFORMATION

Visit North Oxfordshire (01295 259 855; www.visit-northoxfordshire.co.uk)