If we were fan casting the next big detective to crack a gritty whodunnit mystery on our screens, David Mitchell from Would I Lie to You? would not be the immediate choice. But the hackneyed expectations of a boozing, troubled detective have been replaced with a new popular prospect: the smoothed edges of a cosy crime caper. Poker Face, Only Murders in the Building, The Thursday Murder Club: we can't move for watered-down deaths that are explained away by docile amateur sleuths in a saccharine setting. Into this murder mystery canon, Mitchell is a much more natural fit.

In the Ludwig he plays John 'Ludwig' Taylor, an agoraphobic, possibly-neurodivergent recluse who passes his days as a professional puzzle maker – or "the Elvis Presley of puzzle-setters", as he's dubbed. This quiet existence is interrupted when his identical twin brother James vanishes.

John's sister-in-law Lucy, played by Anna Maxwell Martin in an enviable wardrobe of autumnal jumpers, enlists his help. This is where things start to get a bit daft, but bear with, because it works in the mood of the show. Lucy sends for John to come to Cambridge, where she unfolds her silly scheme: John is to walk into the picturesque university town's police station posing as his detective brother, so he can get in for a good snoop of the office and skedaddle with his brother's trusty notebook.

You know what they say about best laid plans. Soon John – as James – is pressed into attending the crime scene of a dead solicitor. There, the puzzle-solving side of his brain takes over and he inadvertently cracks the case. ("Bit awkward really," he tells Lucy through his ancient Nokia brick. "I think I might just have solved a murder.")

So starts a murder-of-the-week mystery with an accidental detective. "How often do people get murdered around here?" John asks. Quite often, it seems, so he puts his puzzle-cracking powers to use. The crime scenes range from a manor estate (classic) and an office (yawn) to a building site (offbeat) and a Cambridge walking tour (inspired).

Any amateur sleuths tuning in to Ludwig may be disappointed on this point. Motive, alibis, red herrings and suspects are inconsequential. The culprit is unguessable up until the moment John shows us his working, probably using spot the difference, or an elaborate process of elimination, or some cipher.

We’re not supposed to be able to work out the crime, but why would we need to try doing so anyway? In a whodunnit you can be confident you'll be told the 'who' of it all eventually.

These weekly cases are more absorbing than the larger question of where exactly John's brother James is, particularly once we start to delve into a boring backstory about their upbringing. But we can forgive all of that because Mark Brotherhood's script is tremendous fun and is matched well with Mitchell's idiosyncratic delivery. You'll be tickled.

Mitchell – whose personality as John is much of a muchness with Mark from Peep Show, but slightly less snarky and imbued with the mental prowess of Will Hunting – would quite clearly be upstaged by Maxwell Martin were it not for the cracking comedic beats. He's also well-matched with his leather jacket-wearing partner DI Carter (Dipo Ola).

The hour-long runtime is a bit of a stretch in a show that pulls the comedy lever more often than the dramatic one, but with just six episodes, it doesn't drag as a whole. It could very well be the most fun you have watching TV this autumn.

Meet the Cast

The new BBC comedy-drama Ludwig introduces us to a reclusive puzzle setter who steps out of his comfort zone to impersonate his twin brother, a Detective Chief Inspector. Peep Show legend and comedian David Mitchell takes on the role of John 'Ludwig' Taylor, who is drawn out of his home when his identical twin brother, James, mysteriously disappears.

In order to find James, he adopts his brother's identity and every aspect of James's life, compelling Ludwig to confront his own issues. Ludwig also has to assist in solving crimes while posing as his brother within Cambridge Police's Major Investigations Team. Ludwig's distinctive way of viewing the world in puzzle form aids him in cracking cases.

Who is who in Ludwig?

John 'Ludwig' Taylor

John is a reclusive puzzle setter who goes by the name of Ludwig in his professional life. When his brother James goes missing, he reluctantly starts to impersonate him to find out the truth about his disappearance, and solves a few murders along the way.

James Taylor

James is John's brother, an accomplished detective with a wife and son. When he goes missing, John steps into his life.

Lucy Betts-Taylor

Lucy is James's wife, who has known both James and John since they were all children together. She recruits John to help her find out what happened to James.

DI Russell Carter

Russell is a new DI at the Cambridge police force, and James's partner at the time of his disappearance. He ends up working side by side with John, unaware that he's an imposter.

DC Simon Evans

Simon is the youngest member of the team at the police force, who lives at home with his mother.

DS Alice Finch

Alice is an ambitious, no-nonsense detective and DCS Carol Shaw's protege.

Henry Betts-Taylor

Henry is James and Lucy's son, and John's nephew.

DCS Carol Shaw

Carol is James's boss, heading up the police force in Cambridge.

Holly Pinder

Holly is an IT technician at the police force.

Chief Constable Ziegler

Ziegler is the imposing chief constable of Cambridge police.

Where to watch Ludwig

Ludwig is available to stream in full now on BBC iPlayer. The first episode of Ludwig aired on BBC One on September 25. Each episode runs for approximately an hour and will be broadcast weekly on BBC One at the same time. The final episode is due to air on Wednesday, October 30.