Arthur Drake Brighton is the eldest son and heir of the noble Brighton family and the elder brother of Edward Brighton. Calm, reserved, and charming, he is an accomplished equestrian who owns a horse named Alexandra. Alexandra participates in competitions, winning an event hosted by an equestrian club during the series, and shows a strong preference, only allowing Arthur and Lynn Russell to ride her.

Arthur shares a long-standing friendship and mutual affection with Sarah Frances Russell that began before Lynn Russell's arrival in England; Sarah develops romantic feelings for him, and their relationship is depicted as steady and supportive throughout the series. Arthur serves as a mentor figure to Lynn Russell, who views him as embodying the ideal of a fairy tale prince due to his noble demeanor and kindness.

Following Lynn Russell's move to England after her mother's death, Arthur becomes involved in her upbringing. He and Edward teach Lynn horseback riding. Arthur's calm presence provides stability during Lynn's struggles to adapt to high society life and the challenges posed by antagonists like the Waverley family. He offers subtle guidance and protection, reinforcing Lynn's aspirations to become a true lady as her mother wished.

After the Russell family's financial downfall and loss of their estate, the Marble Mansion, Arthur's relationship with Sarah remains intact. His involvement in Lynn's later life, including her eventual marriage to Edward Brighton, is not explicitly outlined. Arthur's character arc focuses primarily on his consistency as a supportive figure. Sequels or spin-offs, including the second season *Hello! Lady Lynn*, do not provide additional information about his background, origins, family history beyond his immediate relationships, or activities beyond the events of the initial series.