Finch was a Freemason and was initiated into Lodge of Hope No. 2153 at Portsmouth on 18 September 1918. He was subsequently a founding member of Royal Marine Portsmouth Lodge No. 6423 when it was consecrated on 23 April 1947, and was their first Senior Warden. The following year he was installed as their second Worshipful Master – on the thirtieth anniversary of the Zeebrugge Raid.