Neither of these excellent brands was the first Royal Navy supplier of rum—this honour goes to Lemon Hart (Lehman Hart) a Dutchman who settled in Penzance originally.
Pathways to Legend | LemonHart Rum has an interesting article on Lemon Hart rum detailing the family business and the association with the Royal Navy in the 17th and 18th centuries.
It’s difficult to source in the UK as is Four Bells—but both as well as Woods are from the Diamond Distillery on the banks of the Demerara river in Guyana.
I can only source the Lemon Hart 151 when in Florida from Total Wine distributors a mega alcohol warehouse.
The 151 is not for the faint hearted!