After disagreements arose between Lincoln and Haisman with the BBC in 1968 over their rights to the Great Intelligence and Quarks, the writers departed from the series and both the Great Intelligence and Yeti were retired. The Great Intelligence and its Yeti minions have since appeared in the 1990s "Virgin Missing Adventures" range of novels and the 1995 Reeltime spin-off production "Downtime". The Great Intelligence returned in the 2012 Christmas Special "The Snowmen", where it is voiced by Sir Ian McKellen, which details the entity's origins. Richard E Grant assumed the role in subsequent appearances in the seventh series of the revived show.