Cromer was a place to which the Brigadier believed UNIT headquarters had once been transported. (TV: The Three Doctors) This became the code name of the file detailing these events. Kate Stewart, the Brigadier's daughter, requested this file when she realized the Eleventh Doctor had encountered one of his other incarnations after going through a time fissure that had appeared in the Under Archive. (TV: The Day of the Doctor)
Cromer was located in Norfolk. (AUDIO: The Stuff of Nightmares)
When the Timewyrm sent Ace into the Seventh Doctor's mind, the landscape at first resembled a pier in Cromer. (PROSE: Timewyrm: Revelation)
Cromer was Mrs Wibbsey's home town. She met the Fourth Doctor there in 1932, where she was controlled by the Hornets. The Doctor took her to Nest Cottage in the 21st century to keep her safe. (AUDIO: The Dead Shoes)
