The thriller detective drama has been adapted from a best-selling book series and has been hailed by fans as the 'best mystery series of all time', now streaming on ITVX.08:46, 20 Jul 2026A detective drama streaming free on ITV has been hailed as the ‘best mystery series of all time’ by fans — and viewers are utterly hooked.‌The mystery thriller is based on a mega-hit 13-book series penned by Oxford author Colin Dexter collectively titled The Inspector Morse Series and is a prequel to the time period and incidents depicted in Dexter’s books.‌Created and written by English television writer Russell Lewis, Endeavour serves as the origin story of Endeavour Morse and follows the beginning of his career as a detective constable, later becoming a detective sergeant with the Oxford City Police CID. Large portions of the series were shot in outdoor locations in Oxford, England.‌Endeavour is the third TV show based on characters from Dexter’s books, with the original series titled Inspector Morse, and starring John Thaw, gracing the small screen from 1987 to 2000. A second spin-off show called Inspector Lewis enthralled audiences from 2006 to 2015, while Endeavour first hit UK airwaves in January 2012.Colin Dexter himself made several cameos across all three series and had even written a clause in his will which banned anyone else from playing the part of the famous detective after his death.‌The author famously said: “We never want to repeat what John has done.“A lot of people connected with Morse didn’t want anyone coming along to say we will try and outdo dear old John. I said I’m not ever going to allow that, full stop.”Before he died, Dexter even made it clear that he did not want any more television series developed after Endeavour based on his best-selling novels.‌Endeavour spans nine seasons and has a total of 36 episodes, and the pilot episode attracted a smashing 8.2 million viewers, making it an easy decision for the executives at ITV to commission a full series. Endeavour’s reigning popularity from 2012 till 2023 ensured it was renewed season after season.Shaun Evans, who was 31 when he took over the renowned Inspector Morse title from the late John Thaw, said in an interview with Digital Spy: “I was aware of the character, but I'd hesitate to say that I was a fan. As soon as I got the call, I read the books and became a massive fan of them.“As soon as I started reading the books, I was like, 'God, this is brilliant'. I started to wonder what kind of character they were going to make him as a youngster, who turned into this [familiar] character in his late fifties. I thought it could be really great.”‌With a smashing 90% critics’ approval rating and 92% audience approval rating average on Rotten Tomatoes across nine seasons, it’s safe to say Endeavour is a critical and audience darling.One critic said of the series: “Very charming, in an understated-English kind of way. It also remains in keeping with the spirit of Morse, and is certainly superior to its sequel.”‌While another reviewer added: “Endeavour is wonderfully entertaining on its own, but what puts it over the top is its loving respect for John Thaw. In that regard, it is a just tribute to a great and beloved actor.”A third critic wrote: “It is a suitably complicated and pictorially engaging work of period suburban mystery.”Audiences have been equally bowled over, with one viewer saying: “Endeavor is The Best Mystery Series of all Time. The Morse prequel tops its venerable predecessors, Inspector Morse and Inspector Lewis.”‌Another fan of the show said: “11 out of 10! A must watch if you’re a Morse fan.”While one viewer posted on IMDB: “In my opinion this is the best English series ever! Absolutely great story lines, great actors... The Pilot episode is just wonderful.”Another IMDB user review says: “As a Morse addict I was sceptical about a prequel, prequels are very much in vogue, not always successful, the likes of Prime Suspect flopped, but Endeavour has continued to exceed my expectations. Please let this run for many years, viewing at its best. 10/10.”Article continues belowWhile one review of the show reads: “Best detective series. One of the best detective that I ever saw and the best that is on television nowadays. You can just feel the old atmosphere through the screen. Amazing actors & music. Feels really authentic. A must watch! ITV please make this series available on bigger streaming platforms like Netflix and Amazon. This masterpiece really deserves a bigger audience!!”Endeavour is available to stream for free on ITVX.