Buchan was born in 1869, the son of Charles Forbes Buchan M.D., a military surgeon.[2] He was educated at Bedford Modern School between 1881 and 1885.[4]
Buchan left the War Office in 1919 and was for many years thereafter Honorary Treasurer of the Navy League and a member of its executive committee during Lord Linlithgow's presidency and when Sir Cyril Cobb was Chairman of the executive committee.[1][7] He was also Honorary Treasurer and Secretary of the Training Ship Stork at Hammersmith[1][8] and in 1926 organised a fundraising Ball in aid of the ship at the Hyde Park Hotel in London.[9] In 1939 he was invested as an Officer of St. John for his work with the Navy League.[10][4]
Buchan was a member of the Royal Thames Yacht Club.[2] In 1898 he married Margaret Hume, the daughter of Captain Walter Hume of North Devon, who predeceased him.[2] Buchan died on 30 April 1954.[1][4]