When Sylvia tests her gun in an Italian meadow it mirrors the famous scene in Day of the Jackal which stars Emilia Fox's father, Edward Fox as a professional assassin.
"Volpe" is Italian for fox.
In Episode 3 Volpe "breaks down" in her mini. The Policeman passing fixes it and tells her it was a loose spark plug. Problem is it's a Mini Cooper D. As in Diesel. So has no spark plugs!
Both sisters have played a forensic pathologist . Tara Fitzgerald in waking the dead and Emilia Fox in Silent Witness.