Although numerous sub-species of house mouse exist, only one is found wild in mainland Britain (Mus musculus domesticus). Since these sub-species cannot be readily differentiated in archaeological material, in this paper (Dobney and Harwood, 1999) the house mouse is simply considered as Mus musculus.
The genus Mus lived originally in the steppes of Central Asia where it is thought to have used rock crevices for shelter, thus pre-adapting it to a commensal existence in and around areas of human habitation. This is supported by evidence from modern populations such as that on the island of Skokholm where it shelters on cliffs in early spring.
On the basis of the fossil record, the house mouse is thought to have been present in England since the Iron Age at the latest. It appears to be competitively inferior to the two native British species of mouse (Apodemus sylvaticus and Apodemus flavicollis) in open farmland and woodland. It is, therefore, principally a commensal, living in and around buildings.
There is no evidence for the presence of the house mouse in the North of England prior to the arrival of the Romans, although this may be a result of the paucity of Iron Age occupation sites that have been excavated in the region and the lack of systematic sieving. The species does, however, appear to have been common in York throughout the Roman and Anglian periods. Outside this urban centre, there are only two records prior to the medieval period: one at the Roman fort of South Shields and one from Carlisle.
Reference: Dobney, K and Harwood, J. 1999. Here to stay? Archaeological evidence for the introduction of commensal and economically important mammals to the North of England, pp 373-387 in Benecke, N (ed.). The Holocene History of the European Vertebrate Fauna. Verlag Marie Leidorf GmbH: Rahden/Westf.