those dates align with 1955
Mau Mau is a British docu-movie made in 1955, that is during the British colony and few years after the Mau Mau (rebel group) uprising which started in 1952.
This cheap docu-movie is made for UK audience and aim was to shock the audience by detailing atrocities made by the Mau Mau cult. The movie can be seen here -
http://www.historicfilms.com/tapes/2101 It is clearly a docu-propaganda movie and precursor of the mondo/shockumentary popular in the 60s and 70s, especially the ones produced by the controversial Gualtiero Jacopetti known for his politically oriented faux documentaries ("Africa Addio" and "Goodbye Uncle Tom").
Note that the same year, another movie called "Simba; the Mark of Mau Mau" was also released, featuring Dirk Bogarde and Virginia McKenna which is much better. The American released one movie called "Something of Value" in 1957 about the same subject (based on a novel) and starring Rock Hudson and Sidney Poitier which is great !