By Stephen Dowling BBC News Online entertainment

Reggae star Jimmy Cliff appears at the festival this weekend

The Cambridge Folk Festival, one of the summer's major music events in the UK, is celebrating its 40th anniversary when it starts on Friday. BBC News Online look at its history and why it is attracting big names from outside the folk world.

Folk music in the UK has long suffered from an anachronistic image - one of bearded old men in chunky knitwear, nodding their heads to plucked guitars and drinking real ale.

The Cambridge Folk Festival, held every summer since 1964 by the Cambridge City Council, has done its bit to try and change the image. It is now sponsored by BBC Radio 2.

This year the 40th festival features folk staples such as young pipe player Jarlath Henderson, folk singer Karine Polwart and Irish folk band Last Night's Fun.

Eclectic mix

But the traditional folk elements are bolstered by a line-up that covers a broad range of modern music - from the classic reggae sounds of Jimmy Cliff to the chilled out modern folk of Beth Orton and the rousing music hall Britpop of The Divine Comedy.

Previous line-ups have included former Clash frontman Joe Strummer, Australian singer-songwriter Nick Cave and Senegalese outfit Orchestra Baobab.

Its eclectic mix seems to have struck a chord. This year the 10,000 tickets available for each day of the four-day event sold out in ten days.

It began in autumn 1964 when Cambridge firefighter Ken Woollard, a member of the local Cambridge Folk Club, was asked to set up a folk music festival.

He drew inspiration from a documentary, Jazz On A Summer's Day, about the 1958 Newport Jazz Festival.

According to the festival's website, he wanted "a festival that preserved the values of the fast evolving folk club movement and expressed his socialist ideals, one which covered a wide spectrum of music, and most importantly had a friendly family atmosphere".

The first festival sold 1,400 tickets - but did not make a profit. It did, however, feature a young folk singer called Paul Simon who had just released a song called I Am a Rock.

The festival grew in size, with Woollard remaining its organiser and artistic director until his death in 1993.

The festival encouraged its acts to appear more than once over the festival, playing on their three different stages.

Joan Baez played the festival in 2000

That character has remained. It is elements like this that give it a completely different atmosphere to the rest of the summer's musical events, says one fan.

Stuart Williams, from music magazine Mojo, has gone every year for the last six years and says the festival's charm is that it is not aimed at the traditional festival tribes.

"It's very chilled and relaxed, it's a family event. It's a unique event where you can see folk and country and new artists coming through, as well as the alternative country artists such as Gillian Welch or Alison Krauss, who have both played.

'Songwriting'

"It's the only major festival I can think of that would have them on."

He says the festival "represents songwriting much more than the other festivals. They're about showmanship and all the rock 'n' roll razzmatazz."

He has not found the festival to be an old-fashioned affair. "The old image of men drinking real ale was exactly what I thought the festival would be like before I went six years ago. But when I got there I was pleasantly surprised."

Joe Strummer was another non-folk star to play the event

Neil Jones, the festival's marketing manager, told BBC News Online its character has partly to do with the fact it is still staged at the Cherry Hinton Hall grounds where it began in 1964.

"If you'd gone back to the Cherry Hinton Hall ground in 1964 you would have seen a very primitive stage - probably quite rickety - and a few hundred people sitting cross-legged in front of it. And all for 12 and 6!"

He says the festival is "the only one in Britain that has its own duckpond.

"You can be in the middle of the festival and you can go for a walk and pretty much be in parkland, because the Cherry Hinton grounds are a park as well."

He said the Cambridge City Council's involvement meant the festival worked hard to introduce new acts to its audience - and keep a relationship with them.

"It's not about getting a whole range of big names so you can make a lot of money. We've developed a relationship with artists.

"Often we will have people play, they will go down well, and they come back a year later and play a bigger stage. People can see how they have developed over a year."