Brittney will play Reverend Will Davenport, "crime-solving partner to Robson Green's Geordie Keating," a news release from ITV said Thursday.
"I am beyond excited. From the moment I heard about the role of Will Davenport, it was something I wanted more than anything. It's a real honor to be joining such a wonderful series, with such a loyal fan base," Brittney said in a statement.
"As excited as I am to be filming a new series of Grantchester, it's also heartbreaking to be saying goodbye to Sidney Chambers," Norton added.
"I've loved this experience, and particularly working with such an extraordinary cast and crew. All the best to the fantastic Tom Brittney in his role as the new vicar. He is a wonderful addition to the Grantchester family."
The show airs under the Masterpiece programming banner on PBS stations in the United States.
Norton announced in April he would be leaving the series after the upcoming, fourth season.
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