The symbol takes the shape of the capital letter L indicating Libra Pondo, which was the basic unit of the Roman Empire. The word libra in Latin means scales or balances.
The symbol is used to represent the pound sterling, the official currency of the United Kingdom and before Great Britain and England. Historians don't know when the horizontal line in the symbol was added for the first time. According to the bank of England museum, there was a cheque written on 7 January 1661 where the sign £ printed clearly. Usually, a simple l letter either capital or small, was used to represent the pound sterling in daily prints until the 19th century.