Trad English slang (1960s, '70s, '80s) mostly used in the South and Central areas of England to refer to someone who is being fooled, a dupe: an idiot, and especially a rich idiot who is being scammed and whose money is being stolen from under his nose.
Thief 1: I've got a little business I'd like to discuss with you.
Stella: Oh, really? And what sort of business would you and I have in common?
Thief 1: That mug you've got in tow... Walter.
Stella: Do you know him?
Thief 1: I've got a bit of interest in him.
Stella: Oh, I see.
Thief 1: See, I know form with you, Stella. You'll take him for every penny he's got and then drop him.
Stella: What I do is my business.
Thief 1: Well, not this time, love. I want that mug kept happy, and when I say happy, I don't want him squeezed dry and ditched. Right?
Stella: Look, I've got more to do with my life than look after some menopausal spendthrift for you.
Thief 1: Yeah, well, this mug's a very important mug. He's worth a lot of money to us.
Stella: And if I don't?
Thief 1: Don't even say it, love. You've got a nice face. So keep it. (The Sweeney, Season 1, Episode 11: "The Big Spender," 1975)