You look up 'skiffle' in the Chambers 20th Century Dictionary and it says "a strongly accented jazz type of folk music, played by guitar, drums and often unconventional instruments etc. popular about 1957". It seems such a slight definition - and yet maybe that fits with the way this music has been sidelined in the history of pop.

There was jazz and blues, country and folk in the skiffle mix - the influences of Leadbelly, Jimmie Rodgers and Woody Guthrie, among others. But in a way it was a punk thing. Back then jazz bands were the alternative to pop and they demanded lots of musicians and more than a modicum of musicianship. But skiffle offered a kind of antidote - there was a DIY ethic involved, that was reinforced by the use of tea-chest bass and washboard for percussion.

The jazz roots were in there nonetheless, and in truth, among its leading practitioners, there was no shortage of musicianship. Lonnie Donegan, for one, was a great vocalist and a multi-instrumentalist who played banjo and guitar in Ken Colger's jazz band, before graduating to play with Chris Barber. Donegan was the leading light in the skiffle 'movement', scoring an astonishing 31 top 30 hits in the UK between 1954 and 1962.

Skiffle marked the first great surge of modern British popular music. It may not have lasted long as a phenomenon but it was hugely influential - The Beatles, Rory Gallagher, Dire Straits' Mark Knopfler, Elton John and Paul Brady are among those who've acknowledged its influence, and it carried through in a direct line into the British blues boom via Alexis Korner, John Mayall and Eric Clapton.

Van Morrison always recognised the importance of skiffle during his formative years, and he provides a genuinely touching introduction to this warm and compelling record. Inspired by Lonnie's superb 1999 Muleskinner Blues album, on which he guests on two tracks, Van brought The Skiffle Sessions together in Belfast - and everyone seems to have had a ball on the night. Anyone who knows the turf will be familiar with the songs, beginning with one of Donegan's most familiar hits 'It Takes A Worried Man', and carrying on through the tunes that inspired a whole generation of blues players: 'Lost John', 'Good Morning Blues', 'Midnight Special', 'Frankie And Johnny' and 'Goodnight Irene'.

It's a record, in a sense, like they used to make them. It's loose and informal, the three principals getting together and doing it for the hell of playing with one another and achieving a memorable type of spontaneous chemistry in the process. Dr John makes a superb cameo appearance on 'Goin' Home' and 'Good Morning Blues', Big Jim Sullivan supplies some sweet licks, but the highlights are undoubtedly provided by the intriguing interchange of vocals between Lonnie and Van.

Lonnie is still going strong at the grand young age of 68, full of impressive swagger and strut. But Van is the man - there's few people on planet earth who can match the depth, power and resonance of his voice in full flow and it comes through here, proud and true, on great versions of 'Good Morning Blues', 'Alabamy Bound', 'Goodnight Irene' and 'The Ballad Of Jesse James'.

The album finishes with 'I Wanna Go Home', a song Lonnie Donegan made his own long before The Beach Boys recorded it as 'Sloop John B'. But then you knew that. Didn't you?