Upstairs, Downstairs is basically Downton Abbey, but it was created in the '70s. The show follows the decline of Britain's aristocracy through the lens of the Bellamy family and their servants. Although the series looks a little dated to modern ideas, its influence on period dramas can't be overstated, and for that reason it deserves the No. 12 spot on this list.
Watch Upstairs, Downstairs on Brit Box or on Amazon Prime Video.