The SMLE, or short magazine Lee-Enfield No.1 Mk III was the mainline rifle with Britain going into The Great War on July 28th, 1914.
It featured a magazine cut-off allowing for single rounds to be fired without engaging the magazine to feed cartridges upon operating the bolt action. This was later changed as the demand for rifles by quantity led to the Mk III* that lacked the cut-off mechanism among other changes simplifying production.
Chambered for the powerful .303 British cartridge, the Lee-Enfield series of rifles would continue to see service into World War 2. It stayed in use with various Commonwealth forces as late as 2019 with the Canadian Rangers before finally being replaced by the C19 rifle.