Midsomer Murders, the TV show that notches up an unfeasible number of grisly killings in picturesque locations in Oxfordshire, is celebrating 25 years with a documentary.

The ITV special explores the appeal and popularity of one of Britain's most enduring crime dramas.

Die-hard fans are now deep into series 22 of the show which first aired in March 1997 and was an immediate hit, attracting 13.5million viewers.

Over the years its eerie Theremin opening music has set the scene for death by cricket bat, fire iron, doped horse, pitchfork, Celtic spear, vintage claret, longbow arrow, and hatpin. There has even been an alien abduction.

The documentary features new interviews from actors John Nettles, who played DCI Tom Barnaby from 1997 to 2011, and Neil Dudgeon who played DCI John Barnaby who took over from his cousin in 2011.

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On his 10th anniversary in the role Neil Dudgeon said: "Usually as an actor if a job goes on for three months it is a long job, if you go to the National you might stay there for a year but the idea that you might be in the same job for 10 years, playing the same character, seems to me to be tremendously unlikely.

"If you are going to work in television as an actor what else would you want to be doing? It’s a fantastic job – wonderful crew, beautiful locations, great scripts, marvellous guests, great fun and nice catering… What more could one ask for?"

Other key cast members feature in the documentary including Jane Wymark, who played Tom's kind wife Joyce, and Jason Hughes who plays John Barnaby's sidekick DS Jones.

The programme tells the story of how the series was adapted for the small screen from Caroline Graham's Chief Inspector Barnaby books, with the first episode The Killings At Badger's Drift.

The documentary also recognises the off-screen talent who have played pivotal roles in keeping millions of viewers glued to their screens.

And it higlights its illustrious list of former guest stars which has included Olivia Colman, Jenny Agutter, Hugh Bonneville, Sanjeev Bhaskar, Imelda Staunton, Alison Steadman, Claire Bloom, Bernard Cribbins, Orlando Bloom and Superman himself Henry Cavill.

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The film also takes viewers behind the scenes of the filming of Series 23, and joins a Midsomer coach tour of the show's filming locations, many of which are in Oxfordshire.

The Lions at Bledlow has been five different pubs, while The Crown in Sydenham is at least three.

Villages around the Oxfordshire/Buckinghamshire border - Turville, Hambleden, Fingest, Haddenham and Long Crendon - are favourite backdrops.

Meanwhile grand country houses such as Mapledurham and Greycourt plus many ancient churches have also been the scene of murderous goings-on.

  • Midsomer Murders - 25 Years of Mayhem is on ITV on Sunday May 29.