"Song of Liberty" is a British patriotic song which became popular during the Second World War.
The song was set to the music of Edward Elgar's Pomp and Circumstance March No. 4. It followed the success of Land of Hope and Glory, another patriotic song with lyrics by A. C. Benson set to Elgar's Pomp and Circumstance March No. 1. In 1940, six years after the death of the composer, A. P. Herbert (with permission) wrote lyrics to the tune.
Lyrics
Herbert wrote two verses for the song, each followed by a refrain "All men must be free / March for Liberty with me ... " from which the song gets its title.
References
Song of Liberty Wikipedia(Text) CC BY-SA