At the age of 18 he was called up for military service, and joined the Royal Air Force, being posted to India in 1945.
The cathedral organist, Malcolm Boyle, encouraged him to apply for the organ scholarship at St John's College, Cambridge, for which he was successful.
Within five years of Guest becoming organist and choirmaster, the whole future of the choir at St John's College came into question, with the proposed closure of the day school which provided the choristers.
[2] Herbert Howells and Michael Tippett are among the many composers who wrote liturgical settings for the St John's College choir whilst Guest was organist and choirmaster.
The famous British baritone Simon Keenlyside was a chorister and subsequently a choral scholar in the choir of St John's College, Cambridge while George Guest was the choirmaster there.