The twenty pence was introduced into the coinage in 1982, eleven years after decimalisation. To make it distinct from the ten pence and fifty pence, it was produced at a size that was smaller than the ten, but the same shape as the fifty – an equilateral curve heptagon. This shape makes it better for vending machines than multi-sided shapes with hard corners.
The design featured the Tudor rose. It was minted from, 1982 until 2008 with this design and it, along with the pound, were the only two coins not to be re-sized in the 1990’s. Minted in sterling silver on just five occasions through that twenty six year period, the design looks superb.