On 10 November 1967, The Beatles had made a promotional film for the single Hello, Goodbye. Since no viola players featured in the clip, they risked contravening a Musicians' Union ban on miming, since it would make it obvious that the music was not all live.
In order to escape censure, a new mono mix was made on this day. It omitted the viola parts, and was subsequently dubbed onto the BBC's copy of the film. However, it was a wasted effort as The Beatles' own performance made it clear that they were miming, and the film was not shown in the UK.
The BBC had planned to show the promo on Top Of The Pops on 23 November 1967, but this was cancelled on the 20th. The official reason was that "a minor portion of the film contravened the Musicians' Union regulations concerning miming on television".
On 21 November, BBC cameramen attended an edition session for the Magical Mystery Tour film, to gather replacement footage, but the 23 November edition of Top Of The Pops instead ran footage from the 1964 film A Hard Day's Night. A combination of footage from the edit suite and still photographs was eventually shown on the 7 December 1967 edition of the show.
Also during this brief session, which ran from 10.30-11am, copies were made of the final mono mixes of It's All Too Much, All Together Now and Only A Northern Song, for the producers of the Yellow Submarine animated film.