The holy grail of house purchase!
This is the Land Registry form on which a mortgagee of a registered title acknowledges that the mortgage has been paid off. Get your hands on one of these and the property is yours with nobody else having a claim on it - always providing you have not secured any bank loans against the property as well as your mortgage. Form DS1 has replaced Form 53.
Get professional help from a qualified independent mortgage advisor and see how much you could save on your mortgage payments. There's no obligation, just plain good advice.
See also: Financial Services, Mortgages