[1] Born in Uppingham, Rutland, his brother was Everard Calthrop, railway engineer.

He entered the London and North Western Railway (LNWR) as a Cadet at the age of 16 in 1886.

[1] In 1910 Calthrop left Britain to become General Manager of the Buenos Aires and Pacific Railway.

During the First World War, Calthrop was seconded by the Government, who appointed him Controller of Mines.

For this service, Calthrop was made a baronet of Croxley House, Hertfordshire in 1918.