Acetate version of Ogre Battle by Queen. This is an edit of their third BBC session take of Ogre Battle from December 1973, most likely intended for a 7" single release. link
Thanks for the links, Gaabiizz and Mayniac - gave it a listen, and I'm not convinced. To me, someone has taken the track and added effects (a la the De Land Lea demos on the 2011 bonus discs) along with the crude cuts, or has taken it directly from an overused BBC vinyl and cut it in length.
Even if it's real (perhaps GB or GT can verify, please?), I'm not sure I see the point.