Earlier this year, British Pathe uploaded its collection of 85,000 archival newsreels, unissued materials, and other films to YouTube. The collection covers the years 1896 to 1976. This collection is an excellent resource for research on Churchill as he appears in dozens of these films.
One of the most interesting of the Pathe films that includes Churchill is the newsreel on the Sidney Street Siege. On January 3, 1911, London police cornered two anarchists in a house at 100 Sidney Street, London and a battle ensued. Serving as Home Secretary at that time, Churchill, in typical fashion, rushed to the scene to observe events firsthand.
Two other interesting videos in the Pathe collection are a newsreel of Churchill inspecting the London docks in 1940 (below) and footage of Churchill visiting the 8th Army in the Egyptian desert with Generals Alan Brooke, Harold Alexander, and Bernard Montgomery in August 1942 (bottom).