Set in Wales, the series will follow John Chapel (Spall), a retired actor who starred in the fictional detective TV show Caesar.

After the death of his neighbour, John teams up with an actual detective sergeant in Janie Mallowan (Gwyneth Keyworth). The two form a funny couple, but, each week, they must negotiate their opposing instincts to solve a murder.

Despite their differences, and all their arguments about the case and their personal lives, they soon come to realise that they are the closest thing one another has to a best friend.

In a similar vein to its cosy crime phenomenon Death In Paradise, whose Caribbean setting has long served British audiences with some tropical escapism, the BBC has said that Wales itself will be providing “various stunning locations” as “a backdrop to their investigations.”

Spall’s casting follows his recent multiple accolades for his heartrending performance as the late Peter Farquhar in The Sixth Commandment.

He said: “I’m relishing the prospect of getting stuck in as we embark on creating this truly oddball detective duo who develop their unusual combined eccentric skills to hilarious and surprisingly successful effect in beautiful rural Wales and its gorgeous towns and villages.”

Writer and creator Paul Doolan likes his unlikely couples, having previously written the RTS Award-nominated Bloods for Sky. Bloods followed the antics of an oddball paramedic partnership made up of Samson Kayo and Jane Horrocks, as they dealt with emergency calls and each other’s foibles.

Simon Hynd, who has directed beloved British sitcoms such as Ghosts and Motherland, will direct the six parts.

Jon Petrie, Director of Comedy at the BBC, said: “This series has all the hallmarks of a BBC Comedy classic; it’s the perfect comedy drama caper which never forgets the funny. We feel thoroughly spoiled to have such a wonderful cast on board.”

Filming for Death Valley will begin in Wales in June 2024. It will air on BBC Two, BBC One Wales and BBC iPlayer.