If there were any more questions to who is the Mole they were answered tonight. Big spoiler:
In the opening credits, after Dorothy is shown and the Mole logo appears, a bunch of random letters appear on the screen constantly switching. Slow mo and you can see "bilL is tHe moLE" on around...
There's a new "Bill is the mole" clue online fans are discussing regarding last night's episode:
In the opening credits, right after Dorothy is introduced, the Mole logo appears. In the mish-mash of letters in the Mole logo, the word "Admiral" can clearly be seen. Bill was an Admiral...
I wouldn't be so sure just because someone deciphered that "clue" that it's 100% fact.
They've established several times that "The mole deceives and lies" and it could be just a red herring. That telegram was from the mole, afterall.