Calderwood was admitted a
solicitor in November 1912 and joined the law firm of Townsend, Wood & Calderwood, of Cricklade Street,
Swindon, Wiltshire. In 1919, he relinquished his commission. He returned to Swindon as a partner in Townsend, Wood & Calderwood, and during the 1920s he sometimes served as a
liquidator. In 1929, his partnership with John Crewe Wood was dissolved and Calderwood thereafter carried on the firm of Townsend, Wood & Calderwood as a sole partner. From the 1930s until his death Calderwood lived at The Hermitage, High Street, Swindon. In 1933, he enlarged the house. In 1935, he donated to the
Borough of Swindon a
chain of office for the
mayoress. Elected to
Wiltshire County Council, he served as chairman of its Standing Orders Committee from 1947 to 1960, as chairman of its Selection Committee from 1946 to 1960, and as
chairman of the Council from 1949 until his death in 1960. He was also appointed an
alderman. Calderwood was for several years a member of the Committee of the
Wiltshire Victoria County History and briefly served as its chairman in 1959–1960. He died at Swindon on 7 February 1960, at the age of 72, and the next volume of
A History of the County of Wiltshire to appear noted that ==Honours==