This is a 13 part documentary, based on the journals of Churchill's bodyguard, Walter Thompson, who served the Prime Minister during WW2, and in years prior. According to this documentary, the journal was heavily censored by British security services when it was first published in 1951. Subsequently, the diary was declassified and Walter Thompson made several short movie documentaries. This is a compilation of all that previous work, plus new material added by the makers of this film. This same firm produced the multi-part documentary on Adolf Hitler's security measures during the same time, as well as a number of other World War 2 documentaries.
Was on channels:
The Marsh King's Daughter 
Terminator 2: Judgment Day 
Police Interceptors