Nimmo's first job in the U.K. was as a planning officer with Westminster City Council from 1986, after which she worked for the surveyors Drivers Jonas followed by KPMG and Manchester City Council (1996) where she was involved in the regeneration of the city after the IRA bombing of 1996. She worked on the redevelopment of Sheffield town centre for Sheffield One (2000) and was design and regeneration director at the Olympic Delivery Authority from 2006 (interim from 2003).