The Cambridgeshire folios are of supreme interest to any student of the Domesday Book because there exist for portions of the county two other versions of the original returns. One of these is the Inquisitio Eliensis which gives an account of the estates held or claimed by the abbey of Ely in the counties of Cambridge, Hertford, Essex, Norfolk, Suffolk and Huntingdon. The other, and even more important, version is the Inquisitio Comitatus Cantabrigiensis which surveys the greater part of thirteen out of the sixteen Domesday hundreds of the county. From the body of the manuscript there is missing a leaf which must have described holdings at a number of places in the hundreds of Longstow and Papworth. The manuscript, too, breaks off abruptly in the middle of describing Northstow hundred and the lost portion must have described the hundred of Chesterton and the two hundreds of Ely. In spite of these defects, what remains surveys the greater part of the upland of southern Cambridgeshire. It was J. H. Round's work on this document that laid the foundations of the modern study of the Domesday Book, and he opened his masterly account, first published in 1895, by saying: ‘The true key to the Domesday Survey, and to the system of land assessment it records, is found in the Inquisitio Comitatus Cantabrigiensis.’

The existence of these two subsidiary documents means that for a great part of the county there is a parallel Domesday account, and for many of the widespread Ely estates even a third account.