Interestingly that would put some UK banks as running code that was written when the currency was still Pounds, Shillings and Pence.

In the past I've heard that some banks put a decimalisation layer on top of their existing business logic, that would translate between the old Pounds, Shillings and Pence currency, and the new decimal currency. I wonder if there are any banks out there which still have Pounds, Shillings and Pence at the heart of the computer systems.

For 10p, 5p and 2.5p quantities, that wouldn't be an issue as following decimalisation, those simply reused the Florin, Shilling and Sixpence coins.

Also yielding:

  0.5p = 1.2d
    1p = 2.4d
    2p = 4.8d
    3p = 7.2d
    4p = 9.6d

(The 2.5p coins, then eventually also the 0.5p "new pennies" went out of circulation.)