When the Domesday Book was taken around medieval England, it needed a cart to itself. Now, in its state-of-the-art electronic form, it can slip into your pocket. With the publication of Domesday Explorer, this most famous piece of medieval accountancy has been transcribed and reproduced in a searchable electronic form for the first time.

Attempts in the United States to be the first to cram the unique records of Domesday on to a disc fizzled out, leaving a team of British historians and computer scientists to cross the finishing line first, after 15 years of research and development.

All the pages of the original, handwritten by a single, unknown scribe, have been scanned and reproduced, and the entire text has been placed on the disc in translation. You can look up a place, a person, a county, an occupation or any other piece of information held in the original.

Why should we still be so interested in the Domesday Book? John Palmer of Hull University, who led the historians working on the project, says it remains unique as a historical record. Never since has anyone sought so exhaustively to list every piece of property and wealth in a country. When it was commissioned more than 900 years ago, chroniclers claimed that “not one ox, nor one cow, nor one pig” escaped the teams of assessors who gathered information about the value of the lands conquered by the Normans - and it was this exacting test of what the country held that earned the book its name as a financial equivalent of the Day of Judgment.

Such was the definitive nature of this financial census that it was used as a reference work by rulers and judges for hundreds of years, taken around England to settle disputes. Many estates, although changing owners, stayed intact for centuries afterwards, and the county boundaries detailed in Domesday remained more or less unchanged until local government reorganisations in the 1970s.

But if you browse through th disc, or at least its translated pages, you begin to glimpse an entirely different social order, one that is much more complex than you might have imagined. For example, while you might have guessed that the largest part of the population were peasants, the Domesday Book specifies 18 grades of peasant, no doubt each with its own degrees of social pretension, distinguishing serfs from villeins, freemen from cottagers, and so on.

The translation also shows that slavery was still common in England, largely as an overhang of the Anglo-Saxon social order, which had been overthrown by the invasion of William the Conqueror in 1066, 20 years earlier. Almost within a generation, slavery disappeared from English society. The Domesday Book doesn’t interpret or comment. It simply provides list after list, showing who owned what, what type of value was attached to the land and what type of people were working on it. It’s like looking at a country as a giant tax return.

And what is absent is as interesting as what is included. We might know that in a village a landowner held property occupied by a dozen villagers, three ploughmen and three slaves, but the only name that is recorded will be the landowner’s.

The CD-Rom has been criticised as a solution in search of a problem. But a project such as Domesday Explorer plays to the strengths of the medium, making the most of its vast storage capacity and almost instant searching potential, plus the visual representation of the elegant pages of the original and other clickable ways of navigating the information, including maps.

This same approach of reproducing medieval manuscripts with an accompanying transcription and commentary has been applied in the publication of the Hengwrt Chaucer, one of the earliest manuscripts of the Canterbury Tales, held in the National Library of Wales.

The leader of the project at the library, Dr Ceridwen Lloyd-Morgan, points out that this allows such historic manuscripts to be made universally available.

Among the discoveries claimed by researchers on this CD-Rom is that Chaucer himself may have been involved in assembling the manuscript and that he had intended the title to be The Tales of Canterbury, rather than The Canterbury Tales.