Most of the notes issued by the note-issuing banks in Scotland and Northern Ireland have to be backed by Bank of England notes held by the issuing bank. The combined size of these banknote issues is well over a billion pounds. To make it possible for the note-issuing banks to hold equivalent values in Bank of England notes, the Bank of England issues special notes with denominations of one million pounds ("Giants") and one hundred million pounds ("Titans") for internal use by the other banks.