Police procedural for my dad

My dad used to only read non-fiction, mostly biographies. He’s in his 70s now and has just stated reading fiction. He’s decided he likes crime fiction, and from me asking him what he likes/doesn’t like about what he’s read so far, I’ve realised he enjoys police procedurals. The more realistic and detailed the better. Ideally more rural than city based. The only thing I’ve read that comes close is Rivers of London, and fantasy is an absolute no for my dad! It’s his birthday next week and I’d love to buy him some books. Help please!