Original sentence: Angleton is notable for both his long tenure as the CIA's foremost "spy catcher" (as Chief of Counter-Intelligence), but also  his successful deception by a Soviet spy, Kim Philby.Angleton's faith in his abilities was deeply shaken by how Philby had so sucessfully fooled him for so long; from that point on he was best known for his exceptional and relentless sensitivity to any sign of further moles within the CIA.When Philby's close associates in Britain's Most Secret Services, MacLean and Burgess, defected, it was immediately clear that Philby had staged a massive and unprecedented long-term espionage ring in both the US and England, directly under the noses of the finest minds in Counter-Intelligence available, including Angleton
Edited sentence: Angleton is notable for having become chief spy catcher at CIA, but having been chiefly deceived by a Soviet spy, Kim Philby.From that point on, Angleton was vulnerable to any suggestion that someone was a spy, and the remainder of his career can be viewed as a struggle between belief that everything is false and mad passion to know the truth.When Philby's close associates in Britain's Most Secret Services, MacLean and Burgess, defected, it was clear that Philby himself had fooled everyone, including Angleton