Admiral Sir Hugh Francis Paget Sinclair,, known as Quex Sinclair, was a British intelligence officer. He was Director of British Naval Intelligence between 1919 and 1921, and he subsequently helped to set up the Secret Intelligence Service and GCHQ.

The Secret Intelligence Service (SIS), commonly known as MI6, is the foreign intelligence service of the United Kingdom, tasked mainly with the covert overseas collection and analysis of human intelligence on foreign nationals in support of its Five Eyes partners. SIS is one of the British intelligence agencies and the Chief of the Secret Intelligence Service ("C") is directly accountable to the Foreign Secretary.