Which army corps does Thomas Barrow join after being caught stealing in series one?

After being caught stealing in series one, Thomas Barrow joins the Royal Army Medical Corps.

Thomas is one of Downton Abbey’s most scheming servants, and his attempts to undermine John Bates repeatedly put him at risk. During the first series, Bates discovers Thomas stealing wine, while Molesley later catches him trying to steal money from Carson’s wallet. Realising that his position at Downton is becoming untenable, Thomas hands in his notice and arranges to join the army.

He chooses the Royal Army Medical Corps partly because war appears imminent and the role seems safer than ordinary front-line service. The plan does not protect him completely: during the First World War, Thomas is sent into dangerous conditions and serves near the battlefield. He deliberately exposes his hand to enemy fire, seeking a “Blighty” wound that will send him home.

The answer is sometimes shortened to “Army Medical Corps,” but Royal Army Medical Corps is the formal name and the canonical answer used for the character. The Royal Army Service Corps, Royal Engineers, and Royal Flying Corps were separate organisations with different duties.