I think the year given (1974) is wrong. In Sideman (p. 186), Jim Rodford writes, "He [Roger Myers] had grand ideas for a big show at the Roundhouse London, a long-time favourite stomping ground for us. The titles of the album tracks [on Circus] relate to various circus acts, and we rehearsed the whole album with these acts devising their routines around us. On April 13th [1975] the gig was sold out, and the show went incredibly well, with great crowd reaction." This seems to be the gig from which this version of "Hold Your Head Up" is taken, although I'm not sure.
At ~4:30, there's a quotation of Fučík's Einzug der Gladiatoren, Op. 68, which has taken on circus associations.
