As we have seen, the annual values given in Domesday entry after entry raise many problems (see pp. 208–31). However enigmatic they may be, the fact that they are normally recorded for more than one date presents the possibility of comparing the earlier with the later, and so of obtaining an idea of changes between 1066 and 1086. We may thus see the effects of the Norman Conquest upon the fortunes not only of individual places but of whole districts.

But it is a possibility that is fraught with difficulties. One of these is uncertainty about the arithmetical accuracy of some entries; thus when we read that the combined values of Bramshill and Swallowfield (Hants., 48) at three dates were 40s, 20s 5d, 25d, can we be sure that 25d was not a mistake for 25s, especially as the mill itself rendered 25d? What is more important is uncertainty about the implications of many entries. When we see such figures as £9, £8, £24 for Newbury (Ulvritone, 62b) in Berkshire, can we be sure that the greatly increased value for 1086 was not the result of an alteration in the composition of the manor? Such alterations may well account for the changes, or apparent changes, in the valuations of many manors. Furthermore, as we shall see, the formulae themselves contain many ambiguities.