[andrewaylett]

UK notes are still an IOU. The note I have in front of me says "Clydesdale Bank PLC promises to pay to the Bearer on demand Ten Pounds Sterling at their office here By order of the Board of Directors". This is one of the few cases where "legal tender" actually has meaning: if I present a wodge of bank notes to Clydesdale (or for Bank of England notes, the Bank of England) saying I want repaid in coppers, I'm obliged to accept legal tender for repayment of the debt represented by my notes. Which in Scotland means pound coins, but in England it probably means I'm getting more (although possibly different) notes back.

Interestingly, Clydesdale's office address isn't shown on the note.