In 1967 Paul McCartney was invited to write the score for a movie, The Family Way, starring Hayley Mills, set around new married life for a young couple (presently unavailable).
McCartney wrote a theme Love Is in the Open Air, which Beatles producer George Martin then developed into a dozen variations...and used to score the entire film, which premiered a year later.
The Family Way original soundtrack
The McCartney & Martin collaboration has now been re-recorded and released on CD.
The Family Way soundtrack, new variations
Reading the Amazon reviews, it would appear that over the years, Paul McCartney's classical works are, on the one hand, sometimes praised by pop fans and on the other, often derided by classical music fans.
I make no comment as I'm completely ignorant about classical music.