Greggs was a bakery shop.
Darlington had a branch of Greggs. When most of the Darlington branch of MIAOW left Earth to stop Anthony Marvelle from reaching the Obverse, Magda activated two sleeper agents who worked for Greggs to assist her with the duties of MIAOW. (PROSE: Enter Wildthyme)
Behind the scenes
Greggs famously began selling meat-free sausage rolls in 2019, which generated a strong reaction from the UK public. This event is alluded to in the novel Legends of Camelot, where Donna Noble reads a magazine from that year which covers the incident, though the story does not identify Greggs as the store in question.