In the first year of junior school, I was in Mrs Phillip’s class. She was one of those teachers who you remember, but, sadly not for good reasons. I was very frightened of Mrs Phillips and the worst part of every week was the tables test… forwards, backwards and questions in between. I still know my tables very well and for that I think I should thank her, but it could have been less traumatic! 

Why did I need to have this grasp of the times tables up to twelve? Well, at that point there were no electronic calculators and no smartphones, so maths had to be done mentally. In order to calculate money in particular I needed to be able to work in base 12 and base 20 because I was a child pre-decimalisation.

Up until 1971 Britain paid for its goods in pounds, shillings and pence. Twelve pennies made a shilling and twenty shillings made a pound (represented as £/s/d). Life was certainly more complicated when calculating money up to 1971.

Fifty years ago, Britain changed to a decimal system with 100 new pence to one pound. 15 February 1971 was decimalisation day...