In 2005, it was announced that Christopher would be stepping down from the sci-fi show after just one series, at which point David Tennant took over as the Time Lord.
A spokesperson for the BBC declined to comment when approached by HuffPost UK.
Since ‘Doctor Who’, Christopher has enjoyed success overseas, appearing in ‘Thor: The Dark World’ and in the dark HBO drama ‘The Leftovers’.
He has also appeared in several BBC productions, including one episode of the 2010 BBC anthology drama, ‘Accused’, for which he won an International Emmy.
More recently, he starred in the 2016 BBC drama ‘The A Word’, playing the grandfather to a seven-year-old boy with autism.