Interesting the admiralty rating, I was led to believe that UK navy vessels had Fasteners of at least 5/8 " diam, because it was unlikely that an untrained rating could strip anything that size or larger.This would be the war/ immed post war period.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod