"While spending the Christmas of 1085 in Gloucester, William had deep speech with his counsellors and sent men all over England to each shire to find out what or how much each landholder had in land and livestock, and what it was worth."
So, according to the Anglo-Saxon Chronicle, began the most impressive cataloguing of the nation's wealth this country has ever seen.
The Domesday Book was completed in 1086. Twenty years previously, William of Normandy had conquered England's lands; now he wanted their tax returns, and he wanted there to be "not one single hide, nor a yard of land, nay, moreover, not even an ox, nor a cow, nor a swine that was not set down in his writ."
The compilation of the Domesday Book was an excuse for King William's tax collectors to pry into nearly every household in England and Wales. People referred to it as 'Domesday' because it meant the 'Day of Judgement', after which there was no turning back. The Crown's fiscal supremacy was total.
Data was as crucial to tax collection in the eleventh century as it is today. For wealth taxes it is doubly crucial - if you aren't aware of possessions, you can't tax them. This is especially important for things like death duties, introduced by the Liberals in 1894 - or in modern terminology, Inheritance Tax (IHT).
For years, politicians on the Left have yearned for the sort of snooping powers enjoyed by King William - the opportunity to send inspectors into every home in the land, noting down every Edwardian corner cupboard and set of family silver. The types of items subject to IHT but which often slip through the grasp of the probate registry.
And now that opportunity might have arrived, thanks to the doggedness of Dr Cable, the Lib Dem business secretary.
Revitalised and emboldened by their relative lack of exposure during the phone hacking scandal, the Liberal Democrats are pushing for a mansion tax in a quid pro quo exchange for the Conservatives' desire to scrap the 50p income tax rate. Nick Clegg is thought to be open to the idea. David Laws, the darling of the Tories, disagrees, but party insiders describe him as "isolated", according to the FT (£).
Following Vince Cable's comments, communities secretary Eric Pickles told the Daily Telegraph that a mansion tax would be a "big mistake" because people are already paying enough tax. Furthermore, politicians would conveniently fail to review it regularly enough, meaning that thousands of homeowners would have to pay it because of the iniquity of fiscal drag. According to the Daily Mail's 'This Is Money' website, during the second quarter (Q2) of 2011, the number of properties for sale for at least £1m was 8 per cent higher than Q1 and 10 per cent higher than Q2 in 2010.
There are any number of things wrong with a mansion tax, not least the fact that £1m hardly buys one a mansion in most parts of the country these days. Also the potential complexity of it is staggering. For instance, King William didn't waste his time trying to value every property in London.
At the end of the eleventh century, England's capital was a convoluted urban warren of 18,000 souls. What would he have thought of it today, its metropolitan expanse home to 12-14 million, with nearly 13,000 per square mile? A chore not worth conquering.
It is the potential for data gathering that most excites politicians of certain shades. This could even have a benefit, in that a centralised valuation of estates throughout the country could contribute to updating bandings for council tax - a long overdue task.
But King William's subjects objected to Domesday for a reason: an Englishman's home is his castle, so it is said, and he does not want the state snooping around in it. A mansion tax could permit the creation of Domesday Book for the twenty-first century, on a scale King William could only have dreamt of.
If you would like to learn more about the original Domesday Book, visit the PASE project, a joint venture between King's College London and the University of Cambridge.
This article originally appeared on the Total Politics website on 25th August 2011.