The new longer-lasting notes - printed on polymer rather than paper and carrying the portrait of former Prime Minister Winston Churchill - are fetching hundreds of pounds online.
The first notes to be printed have a serial number starting with AA01, followed by six digits.
Not all of the notes have made it into circulation yet, so it’s possible that lower-numbered notes may still appear in cash machines before they make it onto n auction websites.
The Queen already has the first of the notes, AA01 000001. Of the 440 million notes being released into circulation, there are a further 999,999 bearing the AA01 prefix
If you don’t have one of the collectors items, the Bank of England is auctioning off a batch of low serial number banknotes at a charity event on October 3.
However, the lowest, with serial number AA01 000017, is expected to fetch around £1,000 - so you might want to just keep checking your change instead.