The Reverend Tom Hereward is the Reverend of Poplar, London, and works closely alongside the nuns of Nonnatus House.
The sixth series reveals that Tom was adopted at birth and, by his own account, had a nice childhood.
Tom is first introduced in the third episode of Season Three where he meets Trixie and Sister Julienne when they are attending a pregnant inmate at a women's prison. Tom becomes a recurring character from that point on and becomes close to Trixie. At the beginning of Season Four, Tom proposes to Trixie and she accepts, but later breaks off the engagement upon learning Tom was going to be assigned to a new parish in Newcastle as she didn't think she'd be able to accompany him and to be the sort of wife a reverend needs.
This led to Trixie becoming an alcoholic, though she later kicked the habit with the help of Cynthia and Alcoholics Anonymous.
In Season Five, Tom starts dating Trixie's colleague Barbara Gilbert though the union is met with some initial opposition from Trixie who seems unable to let Tom go. She later gives the relationship her blessing, although she is still sad not to have anyone of her own to love.
In the 2016 Christmas Special, Tom accompanies some of the nuns and nurses from Nonnatus House on a mission to South Africa, and at the end becomes engaged to Barbara. He also divises a way to bring fresh, clean water to Hope Clinic. He and Barbara get married in the last episode of Season Six with Barbara's father, himself a clergyman, conducting the service.