The coins have been dubbed the 'holy grail' of change collecting and if you find one it could be worth a lot more than 20p ...
A minting error on a small number of 2008 twenty pence coins has made them highly desirable, with some expected to sell for as much as £100 at auction.
An unusual coin could net its owner over 250 times its face value after an error when it was made. The rare 20p coin was one ...