Original sentence: Philby belonged to the spy ring known as the Cambridge Five, along with Donald Maclean, Guy Burgess, Anthony Blunt and John Cairncross, although Cairncross's involvement has never conclusively been established and several others, including Sir Roger Hollis, former head of the Secret Intelligence Service (MI6), have been suspected at one time or another to be the 'fifth man'
Edited sentence: Philby belonged to the spy ring known as the Cambridge Five, along with Donald Maclean, Guy Burgess, Anthony Blunt and John Cairncross, although Cairncross's guilt has never conclusively been established and several others, including Sir Roger Hollis, former head of the Secret Intelligence Service (MI6), have been suspected at one time or another to be the 'fifth man'