All crime thriller duos, in books or on screen, stand in the shade of Sherlock Holmes and Dr Watson: the contrast between the lone genius and the baffled everyman narrator, the bickering friendship, the rational and the irrational. But Holmes is an amateur detective and Watson isn’t a detective at all. What about when the duos are both professional police officers? Then the dynamic changes. Here are five of the best.

Chief Superintendent Dalziel and Detective Sergeant Pascoe

A duo must really be a duo. You can imagine Morse without Lewis but Reginald Hill’s wonderfully varied books depend on the relationship between the Falstaffian excesses of the boss and the relative sanity of his assistant.

Lethal Weapon

In the eighties there was a sudden wave of cop buddy movies: a white cop paired with a black cop, a man with a woman, an American with a Russian. In 1989 there were two movies about a police detective and a police dog. Tom Hanks was in one of them. They generally haven’t worn well. Lethal Weapon has its problems but Danny Glover is great and it’s the role that made Mel Gibson a star (before he became his own problem).

Carter and Regan in The Sweeney

Our heart wanted to choose Cagney and Lacey (female detectives were a revolutionary idea in US TV in 1981 and they took a lot of heat for it) but the show wasn’t quite good enough. There’s never been anyone quite like John Thaw and Dennis Waterman’s Flying Squad officers, more thuggish than the wrong ‘uns they regularly beat up. Seventies grunge that still stands up.
 

The Bridge
 

This Danish series experimented with two pairings: the psychologically inexpressive female detective Saga Norén was first paired with the over-emotional Martin Rohde. The result was extremely powerful and increasingly moving. In the final two series she was coupled with a detective even more damaged than she was. Returns were sadly diminished.
 

Tony Jordan and Carol Hill
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Brilliantly, instead of Holmes and Watson, Val McDermid’s series gives us the two sides of Holmes. Jordan is the tormented visionary, Carol Hill the skilful investigator. Like the best duos, they are roped together like mountaineers.