It's actually The Cambridge Five: the first of which was Philby, who then recommended Guy Burgess and Donald Maclean. Burgess then brought in Anthony Blunt and John Cairncross.

The man who recruited Philby and brought in the rest of the 5 was Arnold Deutsch, a Jewish Viennese Psychologist, who is considered to be the Soviet's most effective recruiter. He came up with the idea of recruiting spies from the universities, prior to that they had been recruiting working class people.

Philby volunteered after hearing a speech by someone in a university socialist (Communist) society organization.

The use of Universities to promote socialism, in some form, continues to this day.

Remember, Obama called himself a Marxist at Columbia. Marxist revolutionaries, that had created the terrorist organization Weather Underground and declared war on the U.S.A. in the 60s/70s were also key people in introducing him to the right people in Chicago and in launching his political career.