Sinclair educated at Stubbington House School, he joined the Royal Navy at 13 in 1886 and entered the Naval Intelligence Division at the beginning of the First World War. He became Director of the Division in February 1919 and Chief of the Submarine Service in 1921. He became the second director of SIS in 1923. Wikipedia*
On the C-SPAN Networks:
Hugh Sinclair has one video in the C-SPAN Video Library; the first appearance was a 2012 Interview.