Richard Wilson (born 7th July 1936) played Dr. Constantine in The Empty Child and The Doctor Dances.
Wilson is currently best known for playing Gaius in the BBC/NBC fantasy series Merlin, which debuted in 2008 in the UK and 2009 in the US. A second season is scheduled to air in the UK in 2009.
He is not related to Richard Wilson who appeared in The Pilot Episode.