Old Town Murders: BBC’s New Welsh Crime Drama Blends Baffling Cases With Friendship and Second Chances

A university professor is murdered. A head teacher is poisoned before mysteriously drowning during a wild swim. Then a triathlon becomes the setting for a bizarre case of mistaken identity.

These are just some of the cases facing DI Glyn Walsh and DS Sion Dearden in Old Town Murders, a new six-part BBC crime drama set against the picturesque backdrop of Tenby in West Wales.

Starring Mark Lewis Jones and Steffan Rhodri, the series combines unusual murder mysteries with a more personal story about two men whose lives have been disrupted by difficult circumstances. Rather than focusing solely on the crimes, Old Town Murders is also built around friendship, reinvention and the possibility of finding a new sense of purpose later in life.

Created, written and executive produced by Matthew Barry, whose previous work includes Men Up and The Guest, the series is being produced by Quay Street Productions for BBC One and BBC iPlayer in a co-commission with BBC Cymru Wales.

For viewers drawn to character-led mysteries such as Midsomer Murders and Grantchester, the new drama offers a distinctly Welsh take on the cosy-crime formula.

A murder brings two old friends back together

The story begins when DI Glyn Walsh unexpectedly returns early from bereavement leave.

Back at work, he finds himself partnered with DS Sion Dearden, an old friend. Their first case together is anything but routine: an esteemed university professor has been murdered.

The investigation takes the detectives beneath the respectable surface of the local university, forcing them to explore its darker side as they try to establish who wanted the professor dead.

But solving the first case does not give them much time to breathe.

More deaths are waiting.

And each one appears to offer an even stranger puzzle.

Poison, drowning and a triathlon mystery

One of the most unusual cases involves a local head teacher.

The victim has been poisoned, yet somehow ends up drowning while wild swimming. The strange circumstances leave Glyn and Sion with two questions to answer: who wanted the head teacher dead, and how exactly did the poisoning connect to the drowning?

Then the investigation moves into entirely different territory when a triathlon becomes the backdrop for a baffling case of mistaken identity.

The BBC has revealed only selected details about the six mysteries, but the cases already suggest that Old Town Murders will favor inventive puzzles over conventional police-procedural storytelling.

The detectives cannot escape each other

Glyn and Sion’s partnership does not end when they leave work.

The two men also find themselves living under the same roof, giving the series an additional source of humor and tension between investigations.

Instead of simply meeting at crime scenes before returning to separate lives, they are forced to deal with one another both professionally and personally.

That unusual arrangement is central to what Old Town Murders is trying to do.

The murders provide the suspense, but the relationship between the two detectives provides the emotional foundation.

Both men are dealing with difficult periods in their lives, and their unexpected partnership gives them an opportunity to discover what might come next.

Mark Lewis Jones plays DI Glyn Walsh

Welsh actor Mark Lewis Jones takes the lead as Glyn.

He is known for appearances in The Crown, Baby Reindeer, Out There and Men Up, among other television projects.

Glyn’s decision to return early from bereavement leave immediately establishes the emotional weight he is carrying into the investigation.

His story is not simply about solving crimes. It is also about rebuilding a life after loss and trying to find direction again.

That makes his growing friendship with Sion particularly important. The series is interested in what happens when a person who thought they knew where their life was heading suddenly has to start again.

Steffan Rhodri joins him as DS Sion Dearden

Steffan Rhodri plays Sion, Glyn’s friend and fellow detective.

British audiences will recognize Rhodri from Gavin & Stacey, where he played Dave Coaches, while his dramatic credits include Steeltown Murders and Men Up.

His previous work with Lewis Jones on Men Up was particularly significant to the development of Old Town Murders. Barry also worked on that BBC drama and subsequently wrote the new series specifically with the two actors in mind.

That history gives the central partnership a natural foundation.

For a crime drama built as much around its investigators as its mysteries, the chemistry between its two leads could be one of its biggest strengths.

A familiar supporting cast

Lewis Jones and Rhodri are joined by a strong ensemble.

Bethan Mary-James plays DC Remy Jones, while Catherine Ayers takes the role of Chief Superintendent Melanie Morris. James Bamford appears as DC Neil Miller.

Julie Graham also joins the cast as forensic biologist Pamela Thomas. Her previous credits include Shetland, This City Is Ours and Time.

The wider cast allows the series to build a police team around Glyn and Sion, giving the investigations a broader world rather than placing every clue and development solely on the two leads.

Matthew Barry wants something warmer beneath the murders

For creator Matthew Barry, Old Town Murders is deliberately more than a conventional crime series.

At its core, he describes the drama as a story about friendship, reinvention and having the courage to begin again later in life.

That idea runs through the central characters.

Glyn is dealing with bereavement. Sion is also at a point where his life is changing. Their professional partnership gradually becomes an unexpected source of friendship and renewed purpose.

The result is a crime drama in which the detectives are not only trying to understand why other people have died. They are also attempting to understand what they want from their own lives.

The team behind Fool Me Once

Behind the series is Quay Street Productions, the company responsible for dramas including Netflix’s Fool Me Once and ITV’s After the Flood. The production is being made for BBC One and BBC iPlayer, alongside BBC Cymru Wales.

BBC Cymru Wales has also emphasized the Welsh identity of the project.

Nick Andrews, Head of Commissioning for BBC Cymru Wales, described the series as where “picture perfect Wales meets murder mystery,” promising a “thrilling, twisty tale.”

That contrast is central to the show’s appeal: beautiful scenery, familiar communities and an increasingly unsettling trail of deaths.

Tenby is more than just a backdrop

The setting could become one of the show’s defining features.

Old Town Murders takes place in modern-day Tenby, the historic seaside town on the Pembrokeshire coast.

The production has also filmed in Cardiff and along the South Wales coastline. Filming in Tenby has included locations around the harbour and other recognizable parts of the town.

Tenby’s beaches, harbour and colorful coastal scenery provide a striking contrast to the increasingly unusual crimes taking place within the story.

That combination of picturesque surroundings and murder mystery is familiar territory for British television, but Old Town Murders gives the formula a distinctly Welsh setting.

A different kind of cosy crime

The appeal of shows such as Midsomer Murders and Grantchester has never been limited to the murders themselves.

Part of the attraction comes from spending time with memorable characters, exploring distinctive communities and attempting to piece together a mystery alongside the investigators.

Old Town Murders appears to follow that tradition while putting its own emphasis on the relationship between its two leads.

The crimes are unusual enough to provide the central mysteries, but Glyn and Sion’s friendship is just as important to the overall story.

Their personal lives continue developing as they move from one investigation to another.

Six episodes filled with unusual cases

The BBC has already offered a glimpse of what viewers can expect from the six-part series.

The opening murder takes Glyn and Sion into the hidden world of academia.

Another case centers on a poisoned head teacher who mysteriously drowns while wild swimming.

Then there is the strange mistaken-identity case connected to a triathlon.

More murders are expected to follow as the detectives continue working across the area.

At the same time, their unconventional living arrangement gives the series a continuing personal storyline alongside the individual investigations.

That structure allows each mystery to develop its own resolution while the relationship between the two detectives progresses across the six episodes.

At its heart, this is a story about starting over

Perhaps the most distinctive element of Old Town Murders is its focus on two detectives who are not portrayed as young officers just beginning their careers.

Instead, the drama is interested in what happens when life takes an unexpected turn later on.

For Glyn, bereavement has changed the future he thought he had.

His decision to return to work brings him into closer contact with Sion, and their shared investigations gradually become something more meaningful than another series of case files.

It gives the drama an unexpectedly hopeful idea beneath its murder mysteries.

Life can change suddenly. People can lose their sense of direction. And sometimes, an unexpected friendship can become the beginning of something new.

A new Welsh mystery takes shape

There is still plenty about Old Town Murders that the BBC has kept under wraps, including how exactly Glyn and Sion’s unusual living arrangement develops and what personal complications will emerge alongside their investigations.

But the series already has several distinctive ingredients: two established Welsh actors with previous chemistry, a creator who wrote the roles with them in mind, a strong supporting ensemble, a series of unusual murder cases and the picturesque setting of Tenby.

Filming began in Wales in 2026, with production taking place in Tenby, Cardiff and along the South Wales coastline. A release date has yet to be announced.

For viewers who enjoy eccentric mysteries, memorable detective partnerships and beautiful locations, Old Town Murders could offer a fresh addition to Britain’s long-running cosy-crime tradition — with friendship and second chances at the center of the story.