What's the series of 1930s detective stories based in the Fens?

[Duck Duck Goose]

It's been driving me nuts all day, and I've tried Googling things like "detective story fenlands" which isn't helping.

It's a series, of detective stories/murder mysteries, written in the 1930s, with a guy who's based in the Fens, and solves crimes, and I *think* he's official (a cop or something) but he could be merely an "person". That's all I remember.

No, it's not Martha Grimes' Inspector Jury, it's from the 1930s. And it's not The Nine Tailors, which was only a one-off, anyway.

[don't ask]

You don't mean Edmund Crispin's Gervase Fen mysteries do you. He was an Oxford professor in the 1940's.

[don't ask]

Margery Allingham's Albert Campion although a London resident spends plenty of time around Suffolk and Essex in the earlier books.

[Duck Duck Goose]

Yes!! Gervase Fen!!

Thank you.

how could I have forgotten that?
it's a senior moment, I guess