[MargaretR]

Wikepedia quote -
"In the 19th century, gold coins were legal tender to any amount, silver coins were not legal tender for sums over 2 pounds, nor bronze for sums over 1 shilling.

This provision was retained in revised form at the introduction of decimal currency, and the Coinage Act 1971 laid down that coins denominated above 10 pence became legal tender for payment not exceeding 10 pounds, coins denominated not more than 10 pence became legal tender for payment not exceeding 5 pounds, and bronze coins became legal tender for payment not exceeding 20 pence."