[sgbuffett]

This was a legacy phrase from long ago.

From bank of England:
"The words 'I promise to pay the bearer on demand the sum of five/ten/twenty/fifty pounds' appear on all of our notes. This phrase dates from long ago when our notes represented deposits of gold. At that time, a member of the public could exchange one of our banknotes for gold of the same value."

Now there is no gold to exchange for....so the phrase is redundant or false