At his confirmation hearings for the post of secretary of state he rode roughshod over his interrogators (“No one has a monopoly on virtue, not even you, senator”).
That means that the evidence that is accumulated in those places must be considered very unreliable because people will, after a while, start to take on board the views of their interrogators.
" Did you write a letter for a colored man as that place to some gentleman in Saratoga Springs? " " Excuse me, sir, if I say that is none of your business, " answered Bass, stopping and looking his interrogator searchingly in the face.
Whatever the truth, the fact that it was Philby's school friend that was sent, and not a proper interrogator, goes to the heart of the good old chap culture that allowed Philby to exist as a double agent for so long.