Following the War, Leslie was appointed Standing Counsel to the Department of Agriculture, becoming an Advocate Depute in 1947.

He was appointed Queen's Counsel in 1949, and in 1951 returned to private practice, having unsuccessfully contested Orkney and Shetland as the Labour candidate in the 1950 general election.

He was appointed a civil Commander of the Order of the British Empire (CBE) in the 1963 Birthday Honours.

[2] In April 1965, he was appointed Chairman of the Scottish Land Court, taking the judicial title,[3] Lord Birsay.

In 1985, he was a founding trustee, along with writer and broadcaster Magnus Magnusson, of the Scottish Churches Architectural Heritage Fund.