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 realised the Eleventh Doctor had encountered one of his other incarnations after going through a time fissure that had appeared in the Under Gallery. (TV: The Day of the Doctor) The Brigadier's Grandfather Captain Archibald Hamish Lethbridge Stewart lived in Cromer with his wife and kids (TV: Twice Upon a Time).
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)