Domesday Book was commissioned by William the Conqueror (1066-1087) at Christmas 1085. It was designed to show who held every piece of land in the newly conquered Kingdom of England. It was known colloquially as the Domesday Book because it was seen as being as final as the Last Judgement and as difficult to conceal things from. The book does not cover the whole country - Cumberland, Durham, Northumberland, and Westmorland were omitted and London and Winchester likewise, along with some other towns. A separate book, called Little Domesday covered the counties of Essex, Norfolk and Suffolk and, despite its name, it is actually bigger and more detailed than the Great Domesday Book containing the other counties.

Domesday Book records that Hugh de Beauchamp, later created Baron of Bedford, held Willington himself, without a tenant. The manor comprised ten hides and had thirteen villagers and eight slaves. These men were heads of household and their number must be multiplied by a factor of at least four to account for wives and children - suggesting a population of about eighty or so.

The manor included a mill worth twelve shillings and a hundred eels. This was clearly a watermill and presumably stood on the River Great Ouse, quite possibly on or near the site of the later mill. There was also woodland for forty pigs. In 1066 the manor had been held by Askell, a thegn of King Edward the Confessor and had been worth £6. This had fallen to forty shillings by the time Hugh acquired it, though the value had risen to £7 by 1086, suggesting investment and careful management. Domesday Book also notes that Askell had held three virgates in Cople in 1066 "which lay in his manor, Willington".

It is suggested by historians that the reason for the general lowering of the value of manors in the area is accounted for by William I's armies coming through Bedfordshire on their way to put down rebellions in the north. They would have lived off the land and no doubt have committed certain acts of vandalism in what was, to them, still alien, even enemy, territory.