Would Gary Keene believe Yang Yi's words? The answer was impossible.
If Gary Keene believed Yang Yi's nonsense, he would be a complete idiot and utterly unfit to be a member of MI5.
But Yang Yi had to talk nonsense nevertheless, even though he knew Gary Keene would never believe it, and as for Gary Keene, he wouldn't make any judgment on Yang Yi's words. He would only jot them down and verify them later. But for now, Gary Keene would not believe a single word Yang Yi said.
What Yang Yi needed to do was to fabricate lies that were credible enough to be worth verifying by MI5, not those so obviously fake that they wouldn't even garner interest for investigation.
Therefore, most of what Yang Yi said was true, except for the fact that he was sent by the CIA leadership, the rest could be said to be true.
Gary Keene was in thought, while Yang Yi looked at him with a serious expression. After a long while, Gary Keene said in a deep voice, "Who is your superior, and who is the mole?"