Roberts was born in Deptford in south London in 1952 and his father worked as a labourer at the local power station and his mother as a cleaner and tea lady. He worked for Nalgo in the the 1980s. His books, including Stalin's Wars: From World War to Cold War, 1939-1953, have been criticised as being too soft on Stalin.
Gaddis is American and wrote The Cold War: A New History. A sample of his writing is here. Apparently his view of the USSR is that it was an expansionist empire from 1917 onwards, ignoring the fact that Trotsky, who advocated world revolution, effectively lost power to Stalin, who advocated socialism in one country, in about 1926.
Also thanks to Walter Schwarz for recommending Guardian journalist Richard Gott's Britain's Empire: Resistance, Repression and Revolt which describes the violence at the heart of colonialism.