I guess my point before the massive inflow of historical data, was that the United States used to have similar wording on currency up until the late 1950s and early 1960s. Legal tender notes (aka United States Notes) until the series 1963 notes stated, "The United States of America will pay to the bearer on demand X dollars." These were issued by the US Treasury, were a direct obligation of the US Government and were legal tender, however the legal tender language also stated they were redeemable in lawful money at the US Treasury. The idea being that the notes were mere substitutes for lawful money which was specie. In the same way, Federal Reserve Notes and National Bank Notes were promises to pay in the same lawful money. Once the United States defaulted on its obligations to pay in specie, all those legends were removed from the currency, so now a Federal Reserve Note just says that it's X dollars, with no obligation explicit, though technically I think all the notes issued are based on US Treasury securities used as collateral, hence our currency is now based entirely on the issuance of debt rather than assets.
I suspect the same is true in the UK, yet the language remains, which I found interesting.