Supersonic was a British children's television music show which featured pop music artists of the day. Launched in 1975 with its first show of Series 1 on Thursday 4 September 1975, it was produced by London Weekend Television for the ITV network and ran for two years. The show typically lasted 30 minutes and was broadcast, firstly, on Thursday afternoons and then moved to a Saturday afternoon slot. The programme was presented by film and music producer Mike Mansfield.

The show was recorded in front of an audience of children at London Weekend's studios. Mike Mansfield doubled up as producer and director, cueing in performances from the studio gallery instead of presenting conventional links to camera.

According to this cutting from Billboard dated 4 October 1975, ABBA were "just back from television appearances in Italy, London (Supersonic) and France (Ring Parad), with a promotion visit to the US planned perhaps for October."

The referenced TV appearances would have been the Italian XI Mostra Internazionale di Musica Leggera and the French Ring Parade where they performed SOS on both shows.

Although I've never heard that they appeared on Supersonic, there's of course every chance they did a performance for the programme whilst in the UK filming for Top of the Pops.  If so, the song would undoubtedly have been SOS.

However, given the abundance of fans with great memories and many YouTube clips of performances by other performers available, I am pretty sure that they didn't actually appear.

NOTE: The first photo above is from another YouTube episode - for illustration.

According to this site selling a DVD collection of appearances, there is no ABBA appearance.  It would appear that the series was repeated on UK nostalgia channel Granada Plus at some point (which is probably where the clips came from for the DVD seller).  So if ABBA were on the show, the clip would have surfaced by now.

So sadly, it appears they weren't on the show. Perhaps it was scheduled but cancelled at short notice which is why Billboard name it in the cutting?  Who knows?!

Thanks to Carl Magnus Palm and Alison Hall and Richard Knight c/o ABBAtalk.