While Williams' popularity had been brief and he was already forgotten by most Americans, John Lennon was a big fan. The Beatles added several numbers by Williams into their stage act, with John always taking the lead vocal. Slow Down was certainly played before fans in clubs in both Hamburg and Liverpool. Once the group started achieving fame, the song was dropped as the act got whittled down. Like many of their old favorites, however, it was revived by the band for an appearance on BBC Radio. Slow Down only made the cut for one episode of Pop Go the Beatles, recorded on July 16th, 1963 and broadcast on August 20th. This can be heard on the collection Live at the BBC, giving us a good idea of how the group probably performed the number on stage except that, on this occasion, John forgets the third verse and merely repeats the first verse in its place.
Why they returned to this song almost a year later at an official recording session is anyone's guess. Unlike some of the other oldies that they had preserved for posterity in a single take, this one took a few more attempts. In fact, they began with three takes of just the backing track before hitting one that was good enough. It was only at this point that George overdubbed his lead guitar part onto take three. John finally added his raucous lead vocal, then double-tracked it, though there were quite a few differences in the lyrics and the timing of various phrases. All of this took approximately half an hour.
On June 4th, as the Beatles began their first world tour, producer George Martin overdubbed a piano part onto the track, thereby adding an element the group never had when playing the song live. It was then mixed for mono and quickly released on the EP Long Tall Sally in the UK on June 19th. The stereo mix wasn't even made until a few days later on June 22nd.
In the US, Capitol Records first released the song on the album Something New on July 20th. Then, although the American market was already flooded with singles featuring songs from the soundtrack of A Hard Day's Night, Slow Down was released as the B-side to Matchbox on August 24th. Matchbox still managed to peak at number 17 on the Billboard chart, and Slow Down hit a respectable number 25.
Post career releases of Slow Down include the compilation album Rock and Roll Music in 1976, the UK version of Rarities in 1979, and Past Masters, Volume One in 1988.