[2] His grandfather was the philosopher and social reformer Keshab Chandra Sen; and his aunt was Suniti Devi, the Maharani of Cooch Behar.

[4] Sen applied for a commission in the Royal Flying Corps in November 1916, but his application was rejected as he was under age.

[4] This time he was successful, and he was awarded a temporary honorary commission in the RFC as a second lieutenant, with effect from 24 April 1917.

70 Squadron RFC, based at Poperinge in West Flanders, Belgium and equipped with the Sopwith Camel.

[10] He returned to India and joined the Indian Imperial Police as an assistant superintendent (junior scale, on probation) with effect from 20 September 1921.

Following the Japanese attack on Pearl Harbor in December 1941, Sen re-enlisted in the RAF, but was unable to find a means to leave Burma.