You beat me to it Glyn!
I have a theory that there must be an awful lot of unseen footage of The Clash hiding away - especially concert footage. The
From Here To Eternity live album is a hotch-potch of tracks recorded at different venues, and the
Live At Shea Stadium (supporting The Who) album and DVD is the only available 'full' concert available. Even that doesn't show the band in their 'pomp', recorded as it was after they fired Topper, and with all the looming divisions that were building up at the time. Terry Chimes fills in admirably (after all, he recorded the drums for the first album) but the dynamic doesn't have that 'spark'.
I'm just not convinced that that's all there is lying around, especially for a band who shone so bright, albeit for such a short while. We have seen other live clips in the
Rude Boy movie, both from the "On Parole" tour (shot from the side of the stage) and from the outdoor "Rock Against Racism" gig (from the rear of the stage). It's hard to imagine that the footage they used in the film was shot specifically for it, and in isolation. With all the sound gear they'd have needed to get usable film footage, it wouldn't have been too much of a stretch to have recorded a whole show.
Mick Jones stated after he finished his (wonderful) remastering for the
Sound System boxset that that was probably his last involvement with The Clash's back catalogue. Even so, I'm still sure that there is some as yet undisclosed film footage hanging around somewhere.