The new polymer £5 notes depicting Britain’s wartime leader, Sir Winston Churchill, have now completely replaced the old paper ones as legal tender.
While animal rights supporters condemned the use of animal fat in the new fiver's production, treasure-hunters greeted the new note with cheer. Rare £5 notes featuring low or unusual serial numbers have sold for hundreds of pounds, with some even selling for thousands.
Here's how to tell how if the note in your pocket is worth more than its face value.
Which serial numbers are valuable?
The best fivers are those from the first batch, with serial numbers starting “AA01”. The rest of the number should be low to guarantee a high price.