In the novel The Moving Finger, Brian is the son of Mona Symmington and Richard Symmington, a solicitor in Lymstock. According to Richard he would begin the next term at Winhays, a prep school. Brian is the older brother of Colin and the stepbrother of Megan Hunter. He enjoys playing with his electric train.
In the BBC 1985 adaptation of the novel, the character is played by Lucy Gleeson. The name is changed to "Robert Symmington".
In the ITV 2006 adaptation of the novel (Episode 2, Series of Agatha Christie's Marple), the character also appears, with the name reverting to Brian. He and his brother make several appearances and the boys sing a song during a after dinner entertainment for the dinner guests of Richard Symmington. However the actor who played him is not credited.