Long before decimalisation, every British schoolchild had to master the £sd system: 240 pence to the pound. It sounds like a mathematical nightmare, but it was a system of beautiful divisibility that had survived since the time of Charlemagne.

The Roman legacy

The abbreviations used for centuries were Roman ghosts:

• £ (L): from libra, a pound weight of silver.
• s: from solidus, a Roman gold coin.
• d: from denarius, a Roman silver coin.

The power of 240

Why 240 pence? Where 100 divides only by 2, 4, 5, 10, 20, 25 and 50, the number 240 divides evenly into halves, thirds, quarters, fifths, sixths, eighths, tenths and twelfths. For a merchant without a calculator, splitting a pound into a third (6s 8d) or a quarter (5s) mattered far more than decimal tidiness.

The shilling and the bob

The shilling of twelve pence was the workhorse of the system, and its name is the one everybody still half-remembers: a bob, a word whose origin nobody has ever satisfactorily explained. It did not actually die in 1971. A shilling was a twentieth of a pound and so was the new five-pence piece, identical in size and value, and old shillings stayed in circulation alongside decimal coins until 1990, when the 5p was made smaller and they were finally called in. The florin lasted the same way, as the ten-pence piece. Two coins named in Latin and Norman French went on being spent for a further nineteen years after the system that made sense of them had gone.