Which of these is NOT a valid denomination for UK coins?

Okay, let's talk about UK currency and why you won't find a 25p coin jingling in your pocket. The UK decimalised its currency in 1971, switching from a system of pounds, shillings, and pence to a simpler system of pounds and pence. While there have been various commemorative coins issued over the years, the standard denominations have remained fairly consistent. You'll regularly encounter 1p, 2p, 5p, 10p, 20p, 50p, £1, and £2 coins in everyday transactions. The 2p and 5p coins are common, and the 50p is easily recognizable with its unique seven-sided shape. However, a 25p coin has never been part of the standard circulating currency in the UK. While other amounts have been issued for special occasions, the 25p has never been a standard denomination. So, while it might seem like a plausible amount, it simply doesn't exist in the world of UK coinage.