Grantchester series 5 should be called "Dark-chester," say Tom Brittney and Robson Green

Green, who plays Geordie Keating, the gruff police detective whom Will assists, said that he personally feels "it's the best series yet, but the themes are quite shocking in terms of what they kind of turn out to be; be it homophobia, be it racism, be it sexual abuse, be it a suicide pact."

"We deal with very dark subjects that in no way deflects from its likability," he told RadioTimes.com. "It's how those themes affect those very, very likeable gallery of folk throughout the series is quite shocking."

He added that he has seen "snippets" of the series so far, and revealed that one particularly dark episode went "beyond the brief of Grantchester," with a shock that "you just don't see... coming". He also teased that the plot-twist would involve a seemingly likeable Grantchester character revealing themselves to be "destructive"...

"It's that whole notion – when you really thought you knew someone really well and then suddenly... you see it today, in the news, on social media, that this righteous person that's actually turned out to be a f**k-wit and an absolute f**king nightmare of a person and a destructive individual," he said, "and with Grantchester you're taken along with these likeable characters and then you just turn out to be destructive individuals, and you don't really see that scenario coming."

Green also revealed that series five will include a "devastating" storyline featuring Geordie's wife, Cathy (Kacey Ainsworth) and her mother, whom Geordie invites to stay at the family home to help out (without first consulting Cathy...).

"The secrets and lies about her life enter the environment and my [character's] wife never told me about it," he said. "It's things we harbour as individuals, they're very simple themes, but played beautifully within this scenario."

Grantchester series five, starring Tom Brittney and Robson Green, begins on ITV, Friday 10th January 2020 at 9pm