She explains that as a young child she played a game with her parents' friends whenever they came to visit.
Apparently they found it hugely entertaining that, when offered a choice between a 50p coin and a pound coin she always took the 50p coin.
One day, her grandfather saw this happening and called her over to explain things:
"You must understand, a pound coin is twice as valuable as a 50p piece, so you should always choose the pound coin."
The future top accountant replied:
"But Grandpa, then people will not offer me any money."