The one penny coin is currently the lowest circulating denomination of the British (decimal) Pound Sterling, after the half penny was demonetised in 1984. It was one of three new coins introduced into general circulation on the 15 February 1971 when the United Kingdom adopted a new decimal currency system. The other two new coins were the 1/2p and 2p coins (5p, 10p and 50p had been introduced earlier).
To avoid confusion between the old and new coinage all three coins initially had the word "NEW" incorporated into the reverse design; this was later removed.
Bronze was replaced for new coins with copper-plated steel in 1992. In 2008, a new design was introduced. The original coins are still current though, and circulate in parallel with the new ones. Coins issued in 1971 have now been circulating for 48 years.
One penny and two pence coins are legal tender only up to the sum of 20p; this means that it is permissible to refuse payment of sums greater than this amount in 1p and 2p coins in order to settle a debt.