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A puisne (pronounced 'puny') mortgage is a Mortgage over unregistered land that is not protected by a deposit of title deeds with the Mortgagee. It is the only legal interest in unregistered land that must be entered on the Land Charges Register to be binding on a purchaser of the estate. 'Puisne' means 'puny' (that is, weak and ineffectual), and this term reflects the ease with which such a mortgage could be surpressed by later dealings with the land.