Not commonly encountered these days, but BSA and others (including Westley Richards?!!) built single-shot centrefire rifles using Lee Enfield actions. That guy on Youtube doesn't know much about much!

Khyber Pass my arse!!
...and 5 on the rear sight means five-thousand yards??? D!ckhead!

Just had a quick look through the catalogues on hand and could only find reference to the Westley Richards version, that hides the socket, or is removed completely, chambered in .32-40 (page 18 of the repro Rodda catalogue).

My friend Ian has a BSA example in .32-40 here in Darwin, that I have had in my hands. Haven't fired it though. Not sure he has yet either.