Came across this article over on the Daily Beatle Blog. Upon the announcement of the re-release of The Rolling Stones Rock And Roll Circus TV special on Blu-Ray, Rock Cellar magazine conducted an in-depth interview with director Michael Lindsay-Hogg who only weeks after finishing the special began work on Let It Be. The entire article is worth a look but the Let It Be stuff occurs towards the end.
https://www.rockcellarmagazine.com/...d-roll-circus-interview-michael-lindsay-hogg/
https://www.rockcellarmagazine.com/...d-roll-circus-interview-michael-lindsay-hogg/