On April 01 1967, The Beatles entered the larger EMI Studio 1 in order to record a reprise of the title song for their upcoming LP. The idea was inspired by the fact that McCartney would usually thank the audience at the concert before the final song to let them know that the show was coming to an end.
Neil Aspinall had mentioned the fact to Paul McCartney and this inspired the song. It took only one day to record with nine takes of the backing as John and George played guitar, Paul on bass and Ringo on drums with George Martin on the harmonium. They all played live as a unit with Paul singing a guide vocal.
Once take nine was completed, vocals by Paul, John and George were added as were some percussion (tambourine and maracas). Finally, some of the audience tape noise was overdubbed onto the beginning of the song with the count-in as well as the end of the song and in various spots throughout.
Take five of this session can be heard commercially in mono on the Apple/EMI 3-LP/2-CD "Anthology 2" set. The same take five can be heard commercially in stereo on the Apple/EMI DVD "Anthology" series.
The mono mix for the original LP was completed on the same day as the recording in nine attempts whereby the stereo mix was completed on April 20 1967 in ten attempts. The mono mix is longer with an extra bar added to the song as well as having Paul's shouting intro louder than on the stereo mix.
Here's an amusing little clip someone put up about the differences with the mono and stereo versions of the reprise on the LP: