It all comes from a film made in 1970 featuring Fairport and Matthews Southern Comfort at the Maidstone fiesta on the 5th July 1970 and was narrated by John Peel. It was originally released as a support film to Pink Floyds 'Live at Pompeii'
It was released as a limited edition video and sometimes crops up on Ebay. Other attractions at the fiesta (not on the film!)were the Blue Eagles Army Helicopter Team, Chitty Chitty Bang Bang, and the PG Tips Chimps, the whole event being opened by actor Paul Temple.
Fairport played The Lark in the Morning Medley, Sir Patrick Spens, Now Be Thankful, Flatback Caper and Jenny's Chickens/The Mason's Apron.
Matthews SC played My Front Pages and Southern Comfort (sung by a very young Iain Matthews) . Well worth a view if you can get hold of a copy.