Born in Leamington, England, Leamington was educated at Upper Canada College, became a barrister in 1849, and was created a Queen's Counsel in 1863. He was a Liberal Member of the Canadian House of Commons for Hamilton in the 3rd Canadian Parliament. He was Treasurer of the Law Society of Upper Canada from 1893 to 1913. He was knighted in 1906 and died in Toronto in 1913.