According to the American's files, Harry was born on July 7th 1937 which means he would be 25 (almost 26) in this storyline. However, in the previous episode, he gave his birthdate as 1932.
Stock mentions Dalby who will send the Soviets information like Guy Burgess and Donald McLean. These two names are real, both were members of the "Cambridge Five", a circle of important personalities formed in the prestigious university who spied for the U.S.S.R. taking advantage of its relevance in the elite society of the United Kingdom. Burgess and McLean were the first to be discovered, in 1951, fleeing to the Soviet Union. Tom Hollander played Guy Burgess in the BBC mini-series "Cambridge Spies" (2003).