Born in Carlisle, Cumberland in 1906, he spent his early childhood in South Africa, where his father served in Military Intelligence in Pretoria, before returning to England.
[3] Getting involved in anti-Nazi politics in Berlin in the early 1930s, he joined the Communist Party of Great Britain.
[4] Back in England, he helped Tom Wintringham set up the Osterley Park training centre in 1940 which taught guerilla warfare and street fighting for the Home Guard before being drafted into the regular army as a private.
The public outcry led to questions being asked in Parliament[5] and an article in the magazine Time.
Slater drew a parallel in The Heretics between the persecution of the Albigensians in France and that of the Trotskyists in 1930s Spain.