Tonton Streaming Upstairs, Downstairs (1971) S1E7 - Magic Casements

Summer 1906: Captain Hammond, a handsome young friend of James', graciously agrees to escort Lady Marjorie to the opera. Feeling a strong mutual attraction, they quickly realize how compatible they are, despite the age difference, Abuzz with gossip, the servants seem to be the only ones aware of what's going on.