The Royal Mint said more than 2.5% of all £1 coins currently in circulation -- approximately 1 in 40 -- are fake. The new pound is being hailed by the Royal Mint as the most secure coin in the world.

"You should also become suspicious when a vending machine keeps on rejecting a R5 coin, especially if it is dated 1994 or 1995 because vending machines are calibrated to reject fake coins," he says.