In 2001, Dr. Who assassinated Queen Elizabeth II while she was making an appearance in Sheffield. The self-doubts of his accomplice Jason, coupled with his own essentially fictional nature, meant that the Queen survived. (PROSE: Head Games)
Charlie Smith told Ram Singh that he was from Sheffield. This pretence had been given to both Charlie and Miss Quill by the Twelfth Doctor so that nobody would become suspicious of their alien nature. (TV: For Tonight We Might Die)
Behind the scenes Edit
The website whoisdoctorwho.co.uk had a list of sightings of the Doctor from which people had ostensibly been submitting to Clive, a conspiracy theorist character from Rose, who had pictures of the Doctor's ninth incarnation on the website, asking if anyone had seen him.
A submission from H.J. Hardeman claimed to have seen "someone very much like him about a year ago". He had tried swapping "Edwardean gear" [sic] at an Oxfam in Sheffield for a pair of jeans and trainers.