Ransley Samuel Thacker, son of Henry Ransley Thacker, was born on 17 Mar 1891. He was educated at Dulwich College, and in 1915 was called to the Bar by Gray's Inn. In 1915, he married Olive Frances Braithwaite, and they had two sons and a daughter. He practised at the English Bar until 1930, when he entered the Colonial Legal Service. His first appointment was in the British West Indies, as Chief Justice and Police Magistrate of St Vincent (MSS. Brit. Emp. s. 396/1). However, suitable educational facilities for his children were lacking, and he applied for a transfer: in 1933, he was appointed Attorney-General of Fiji, a post he held for five years (MSS. Brit. Emp. s. 396/2). He served as a Member of the Legislative and Executive Councils and as Chairman of the Native Regulations Board. From Sep 1935 until the following Jul, he acted as Chief Justice of Fiji and Chief Judicial Commissioner for the Western Pacific. In Oct 1937, he was appointed King's Counsel (KC) for the Colony of Fiji.

In 1938, he received the appointment of Puisne Judge of the Supreme Court of Kenya, and served in this capacity until his retirement in 1952 (MSS. Brit. Emp. s. 396/3-5). During these years, he was also a Member of the Court of Appeal for Eastern Africa and, on several occasions, he acted as Chief Justice. In 1948, his wife became increasingly ill; she died in England at the end of Aug.

After his retirement in 1952, Judge Thacker continued to live in Africa. He died in Rhodesia (Zimbabwe) in Dec 1965.