in old money

Don’t forget, the fourth round draw is coming up at 1530 GMT. Ten minutes’ time in old money…
– I wonder if there is some story behind the expression.
Thank you.

For a while after the British currency was decimalised in 1971, people would continue to convert back to the familiar “old money” (i.e. pre-decimalisation money). For example, someone complaining about high prices might say “Fifty pence!! That’s ten shillings in old money!”. Your quote humorously uses “old money” to mean “more familiar and understandable way of expressing a quantity”. While “1530 GMT” looks complicated, “in ten minutes’ time” is clear to everyone.