BBC Three (in-universe)

BBC3 was launched in 1969, with its initial broadcast showing the British Rocket Group and Mars Probe 7. (PROSE: Who Killed Kennedy) Dame Emily Shaw saw her daughter Liz Shaw over John Wakefield's shoulder immediately before the launch of the Recovery 7 several days later. (AUDIO: The Last Post)

It broadcast a documentary on Devil's End, (TV: The Dæmons) enitled The Passing Parade: Live from Devil's End, (PROSE: "BBC 3 Schedule") prior to the uncovering of the Devil's Hump. (TV: The Dæmons) The show was presented by Alastair Fergus, and he was joined on air by Professor Gilbert Horner. (PROSE: "BBC 3 Schedule")

James Stevens contacted BBC3 to expose the secrets of the Glasshouse, and they sent a camera crew to where it was located. However, the Glasshouse was abandoned when they arrived. (PROSE: Who Killed Kennedy)

Jo Grant later watched a documentary about a cult in Utah on BBC3, which "gave [her] the creeps." (AUDIO: The Many Deaths of Jo Grant)

On the Inferno Earth BBC3 broadcast the documentary series Occult Secrets of the Nazis. (PROSE: Still Lives)

On 25 December 2010, BBC Three broadcast John Fuchas' film adaptation of The True History of Planets. (PROSE: Mad Dogs and Englishmen)

Behind the scenes
At the time The Dæmons was produced, only two BBC television channels were in operation, the existence of a BBC 3 was intended to suggest a future timeframe (see UNIT dating controversy).

In the real world 1970s plans did exist for a third BBC analogue network, but were ultimately shelved in favour of the IBA's second network Channel 4.

In the script for the ultimately unproduced 1993 film The Dark Dimension, a BBC3 news reporter named Tony McCabe is said to have been killed at Oxford Circus.