Is the former ambassador a shit, a cad or a rat?

The bad behaviour of Sir Christopher Meyer, former ambassador in Washington, raises interesting questions of nomenclature. Should he be called a shit, a cad or a rat? I rather rule out rat as being tabloid-speak, and Meyer, though he has a lot to do with tabloids (as chairman of that humbugging body, the Press Complaints Commission), and actually flogged his memoirs to one, is not himself tabloid material, being dull and colourless. The Sun and the Mirror often refer to men who deceive their wives as ‘love-rats’. How do they refer to a red-haired tabloid editor who gets drunk, beats up her tough-guy actor husband and spends the night in a police cell? The answer is that they simply kill the story.

Leaving rats aside, for the time being, is Meyer a shit or a cad? I recall Evelyn Waugh debating this point in the case of Tom Driberg, who did odd jobs for MI6 and the KGB, and double-crossed both.