First episode without Sykes the dog.
Sykes was a rescue dog, and according to an episode of "Behind the Scenes Doc Martin", Sykes' owner and trainer also trained the dogs in the Doc Martin series.
The murder weapon in the first killing is a British Army FV433 Abbot SPG 105 mm self-propelled artillery piece. Technically not a tank, but more properly self-propelled artillery.
Blake Keswick is played by an actor named Christopher Colquhoun. In the season 11 episode "Blood Wedding", there is a character named Randall Colquhoun. In that episode, a lot of fuss is made about the pronunciation of his surname.
Just a few minutes in, during the celebration for the reopening of the village, Corina Craven tries to get Finn to dance with her. He responds, "I'm not in the mood." The music playing in the background sounds like "In the Mood," originally recorded by Glenn Miller, but is actually "GI Boogie."