In pre-decimal days (before 1971) £1 was broken down into 20 shillings (as it sort of still is today) that consisted of 12 old pennies to the shilling (1/-). Then good old metric supposedly came in to make it easier for the rest of the world to understand it and 1 shilling became 5 new pennies. So 12 old pence equalled 5 new pence (still with me?) which was still a shilling (20 to a £1). 2/6 was an old half a crown, 5/- (shillings) was a crown (25 new pence) hence 2/6 equalled 12 1/2p ..... Hope this makes more sense. It has been explained a few times on here but..........