Tapio Minkkinen writes on the Travelers in Time mailing list
The show was then verified as The Greyhound in Croydon on 21st of November 1971 on the Look At Yourself tour. The recording is ca. 30 minutes longs, it includes only two songs but these are among the longest and most legendary Heep Songs: Salisbury & July Morning.
This is a signicant find because it's a proof of something I wasn't aware of that they played Salisbury live even after the tour. Also this is the earliest live recordind of July Morning to surface. Enjoy!