George gained custody of Peter, who was taken from his biological mother and brought up by his adoptive paternal grandmother, Laura Finch (formerly Black) in Vaucresson, France. In 1925 Laura took Peter with her to Adyar, a theosophical community near Madras, India, for a number of months, and the young boy lived for a time in a Buddhist monastery. Undoubtedly, as a result of his childhood contact with Buddhism, Finch always claimed to be a Buddhist. He is reported to have said: "I think a man dying on a cross is a ghastly symbol for a religion. And I think a man sitting under a bo tree and becoming enlightened is a beautiful one."
In 1954, the Australian journalist and author George Johnston wrote a well-researched series of biographical articles on Finch, his life, and his work, which appeared in the Sydney Sun-Herald on four consecutive Sundays, which were certainly the first detailed account of Finch's life to be published. Finch later provided the inspiration for the character Archie Calverton in Johnston's novel, Clean Straw for Nothing.
However, he was then cast as an Australian soldier in A Town Like Alice (1956), which became the third most popular film at the British box office in 1956 and won Finch a BAFTA for Best Actor. He followed it with The Battle of the River Plate (1956), playing Captain Hans Langsdorff. This was also successful financially and British exhibitors voted Finch the seventh most popular British star at the box office for 1956.
He was soon cast in his first British movie, playing a murderous actor in Train of Events (1949). Critic C. A. Lejeune praised his work in the London Observer commenting that he "adds good cheekbones to a quick intelligence and is likely to become a cult, I fear." The Scotsman said "he should be regarded as one of the most hopeful recruits to the British screen."