Following his departure, Ian has been name-checked on a number of occasions in the series: He was mentioned by Vicki in episode one of The Time Meddler; by the first Doctor in episode four of The Massacre of St Bartholomew's Eve and again by his third incarnation on Spiridon in episode one of Planet of the Daleks. Ian was also mentioned in episode one of the 1993 Children In Need charity special Dimensions In Time and again in Death of the Doctor, a two part story in the fourth series of The Sarah Jane Adventures. After meeting Jo Grant and the Eleventh Doctor, Sarah Jane Smith reveals that she has researched the lives of some of the Doctor's earth-bound companions and discovered that Ian and Barbara have married each other, become professors, live in Cambridge and are rumoured to have not aged since the 1960s. In the 50th Anniversary Special "The Day of the Doctor", the sign for Coal Hill Secondary School identifies the Chairman of the Governors as I. Chesterton. In the spin-off series Class, it was revealed in the episode "Brave-ish Heart" that the Board of Governors had been removed when the school was refurbished as an Academy.
