Page "Cambridge Five" Paragraph 6

Philby learned one of the suspects was Maclean.

Realizing he had to act fast, he ordered Burgess, who was on the embassy staff as well and living with Philby, to warn Maclean in England, where he was serving in the Foreign Office headquarters.

Burgess was recalled from the United States due to " bad behaviour " and upon reaching London warned Maclean.