HM Land Registry 1 is the department of the United Kingdom government reponsible for maintaining the Land Register of England and Wales. (Scotland and Northern Ireland as distinct legal jurisdictions have their own arrangements.) It was initially estbalished in 1862 and is now the responsibility of the Lord Chancellor.
Its main purpose is to record the ownership of, and dealings, (essentially sales or mortgages) with registered land in England and Wales, and it currently holds the records for some 15.5 million properties. This does not amount to every piece of land as it is only since December 1990 that registration has been compulsory, and compulsion is only effective when property changes hands; hence there remains a significant, if declining, rump of unregistered land.
It is entirely self-financing, in that the fees it charges cover the costs of providing and maintaining the register. This means that every purchaser of property has to fork out a few hundred pounds in fees, but on the plus side HM Land Registry will guarantee good title to the land.
It maintains a website at www.landreg.gov.uk which however, does not give access to any live data (for that you have to open an account and go to www.landregistrydirect.gov.uk) but it does provide information on the average prices of residential property (thereby providing plenty of discussion points for that very British obsession with property prices.
Interesting trivia: land parcel #1 on the Land Registry is Chantry Park, Ipswich, Suffolk. and facsimile of the entry hangs on the wall of the local council offices. (With thanks to WolfDave
1 or Cofrestrfa Tir EM as its website proudly announces since, as an agency of the government it is obliged to give the Welsh Language equal status. The 'HM' is of course an abbreviation for His or Her Majestie's
2 Sourced from the obvious places.