Prelude on St Columba is #8 in Willan's "Ten Hymn Preludes", published by Peters, and dating from 1956. St Columba is usually used for the hymn The King of Love My Shepherd Is.
The King of Love My Shepherd Is is an 1868 hymn with lyrics written by Henry Baker, based on the Welsh version of Psalm 23 and the work of Edmund Prys. It is sung to three different melodies: Dominus Regit Me, a traditional Irish tune called St. Columba, and Remsen, the Welsh original.
Dominus Regit Me by Willan is here;
http://www.contrebombarde.com/concerthall/music/33337
The Tune St. Columba is named for the Irish saint who “carried the torch of Irish Christianity to Scotland” (and who has the dubious distinction of being the first to report a sighting of the Loch Ness monster, in 546). The tune is one of the Irish melodies collected by George Petrie (1789-1866).
The Canadian Encyclopedia says this about the "early" organ works of Healey Willan (1880-1968): With the music for organ one enters a different world. Here Willan was thoroughly at home and made a significant and lasting contribution. One work stands out: the monumental "Introduction, Passacaglia and Fugue" of 1916. The Preludes and Fugues in C minor and B minor and the "Epilogue" are the other major works from this period. While not exploring the possibilities of the instrument as searchingly as his masterpiece, they are idiomatic and very typical of their time. They combine an innate Englishness (with a Stanfordian flavour) and a European chromaticism that can be found in Reger and Karg-Elert.
Born in England, Willan became organist-choirmaster of Toronto's largest church, St. Paul's, Bloor Street, but it was his royalties as a composer which allowed him to leave "low church" St. Paul's in 1921 and to become Precentor of the Church of St. Mary Magdalene (Toronto).