Paul McCartney's French horn impression

This video of him performing "For No One" in a studio apparently comes from the movie "Give My Regards to Broad Street." For the recorded version of the song the French horn solo was performed by Alan Civil:

During the session, McCartney pushed Civil to play a note that was beyond the usual range of the instrument (on an F horn, it is the D# on the second ledger line above the staff). The result was the "performance of his life," high praise for someone who was known as the best French horn player in London at the time.

Found at Anything and Everything.