The hymn "I Vow to Thee, My Country" is sung to a tune adapted from which larger work?

Often sung at Remembrance Day services, and state occasions both happy and sad (including both the wedding and the funeral of Princess Diana) this hymn has a text by Cecil Spring Rice (1859-1918) who was, in fact, a high-ranking diplomat and not a poet. Originally the poem was called "Urbs Dei" (City of God) and addressed the issue of a soldier's loyalty to both his earthly and heavenly kingdoms. Although he endorsed WW1 (and encouraged President Wilson to end American neutrality) he adapted the original version of the poem to a more sombre tone to reflect the suffering of war.

The famous composer Gustav Holst (1874-1934) adapted "Jupiter" from the "Planets" as the setting for the hymn.

It has remained popular ever since, and is often suggested as an alternative British national anthem; having a less turgid tune than "God Save the Queen" but being less jingoistic than "Land of Hope and Glory". However, it is not without its own controversy, as some say it, too, endorses colonial attitudes and would also suggest that the notion of a human being capable of perfect love is heretical.