Tom Branson is the Downton Abbey chauffeur who later becomes part of the Crawley family. He begins the series as an Irish chauffeur employed by the household and is initially positioned firmly among the servants rather than the aristocratic family.
Tom’s political views set him apart from the Crawleys: he is an Irish nationalist, a socialist and a republican. His relationship with Lady Sybil gradually changes his place in the story. Despite Robert Crawley’s reservations, Tom and Sybil marry and leave for Ireland.
After Sybil dies in childbirth, Tom returns to Downton with their daughter, Sybbie. He struggles with his changed social position but eventually becomes the estate’s land agent, helping modernize Downton and taking on responsibilities associated with the Crawley family.
Henry Talbot is a later romantic connection for Lady Mary, Joseph Molesley is a valet and footman, and John Bates is Robert’s valet. None is the former chauffeur who joins the family.