Question: Upon which book series is the British television detective drama in which Laura Howard played the role of Cully Barnaby based?

Context articles: Endeavour (TV series)
List of Midsomer Murders episodes
Laura Howard
Lewis (TV series)
Rebus (TV series)
Midsomer Murders
The Enigma Files
Barnaby Jones
List of Endeavour episodes
Prime Suspect 1973

Endeavour is a British television detective drama series.
 It is a prequel to the long-running "Inspector Morse" and, like that series, is set primarily in Oxford.
 Shaun Evans portrays a young Endeavour Morse beginning his career as a Detective Constable with the Oxford City Police CID.
 The series is produced for ITV as a Mammoth Screen and Masterpiece co-production for ITV Studios.
 Following a pilot episode in 2012, the first series was broadcast in 2013, the second in 2014 and the third in January 2016.
 A fourth series was ordered by ITV, began filming in late spring 2016, and premiered on 8 January 2017.
"Midsomer Murders" is a British television detective drama that has aired on ITV since 1997.
 The show is based on Caroline Graham's "Chief Inspector Barnaby" book series, as originally adapted by Anthony Horowitz.
 The current lead character is DCI John Barnaby (Neil Dudgeon), who works for Causton CID.
 Dudgeon's character is the younger cousin of former lead character DCI Tom Barnaby (John Nettles).
 Dudgeon first appeared as randy gardener Daniel Bolt in the Series 4 episode "Garden of Death".
 Dudgeon permanently joined the show in 2011 following Nettles' departure.
Laura Howard (born as Laura Simmons in Chiswick, London, 1977) is an English actress.
 She is probably best known for her role as Cully Barnaby in the long-running British crime-mystery Police procedural "Midsomer Murders".
Lewis is a British television detective drama produced for ITV.
 It is a spin-off from "Inspector Morse" and, like that series, it is set in Oxford.
 Kevin Whately reprises his character Robert "Robbie" Lewis, who was Morse's sergeant in the original series.
 Lewis has now been promoted to detective inspector and is assisted by DS James Hathaway, portrayed by Laurence Fox, who became promoted to inspector in the eighth series airing in 2014.
 The series also stars Clare Holman as forensic pathologist Dr Laura Hobson, likewise reprising her role from "Inspector Morse", and Angela Griffin as DS Lizzie Maddox.
Rebus is a British television detective drama series based on the "Inspector Rebus" novels by the Scottish author Ian Rankin.
 The series was produced by STV Productions for the ITV network, and four series were broadcast between 26 April 2000 and 7 December 2007.
 The first series starred John Hannah as DI John Rebus; and was co-produced by Hannah's own production company, Clerkenwell Films.
 After Hannah quit the series, the role of Rebus was re-cast, with Ken Stott appearing as Rebus in three subsequent series, which were produced in-house by STV.
Midsomer Murders is a British television detective drama that has aired on ITV since 1997.
 The show is based on Caroline Graham's "Chief Inspector Barnaby" book series, as originally adapted by Anthony Horowitz.
 The current lead character is DCI John Barnaby (Neil Dudgeon), who works for Causton CID.
 Dudgeon's character is the younger cousin of former lead character DCI Tom Barnaby (John Nettles).
 Dudgeon first appeared as randy gardener Daniel Bolt in the Series 4 episode "Garden of Death".
 Dudgeon permanently joined the show in 2011 following Nettles' departure.
The Enigma Files is a British television detective drama that ran for one series of fifteen episodes in 1980.
Barnaby Jones is a television detective series starring Buddy Ebsen and Lee Meriwether as a father and daughter-in-law who run a private detective firm in Los Angeles, California.
 The show was introduced as a midseason replacement on the CBS network and broadcast from 1973 to 1980.
 Halfway through the series run, Mark Shera was added to the cast as the cousin of Ebsen's character, who joins the firm.
 William Conrad guest-starred as Frank Cannon of "Cannon" on the first "Barnaby Jones" episode, "Requiem for a Son", and the 1975 two-part crossover episodes, "The Deadly Conspiracy".
 The series was produced by QM Productions (with Woodruff Productions in the final two seasons).
 It had the second longest QM series run (seven and a half seasons) following the eight years of "The FBI".
 The series bore the Quinn Martin trademark where commercial breaks divided each episode into 4 "Acts" concluding with an epilogue.
 The opening credits were narrated by Hank Simms.
Endeavour is a British television detective drama series created by Russell Lewis and co-produced by Mammoth Screen and Masterpiece in association with ITV Studios.
 It first aired on ITV in the United Kingdom on 2 January 2012, and on PBS in the United States on 1 July 2012, as part of the Masterpiece Classic anthology.
 Four series have been made, the fourth airing at the beginning of 2017 in the UK and Ireland.
 s of 29 2017, episodes of "Endeavour " have aired.
Prime Suspect 1973 (also known as Prime Suspect: Tennison) is a British television detective drama series, and a prequel to the long-running "Prime Suspect" series, originally starring Helen Mirren as DCI Jane Tennison.