apparently they played it because it was a favourite of Brian's.
if you don't want to pursue bootlegs, RankOutsider, the track is in the film Stones in the Park, which is an official release, at least in Europe. whether or not they played it (or anything else) "well" that day, those renditions have really gotten under my skin - in a good way, i mean.
"What do you want - what?!"
- Keith