In the novel The Moving Finger, Colin is the son of Mona Symmington and Richard Symmington, a solicitor in Lymstock. Colin is the younger brother of Brian and the stepbrother of Megan Hunter. He enjoy fishing even though most times he didn't catch any fish and only got wet. An anonymous letter stated that he wasn't Richard Symmmington's son, but this was not true. He does not look like his parents or his brother, and had bright red hair.
In the BBC 1985 adaptation of the novel, the character is played by Stuart Mansfield. The name is changed to "James 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 James. 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.