Dempsey and Makepeace (1985)

A street-smart New York lieutenant is sent to London and paired with Detective Sergeant Lady Harriet Makepeace, an aristocrat who is every bit as stubborn as he is. Michael Brandon and Glynis Barber play the culture clash for sparks, and the chemistry was real enough that the two actors later married. It is pure 1980s ITV action, with car chases and big hair, so come for the pair rather than subtle plotting.