After World War One, the British looked at how to apply the lessons of the war to development of a new infantry rifle. Even before the war, a decision had been made to move to an aperture type rear sight - which would have been used on the Pattern 1913 Enfield, had the war no interrupted adoption of that model. So after the war, trials were made on some MkIII SMLE rifles refitted with rear aperture sights. These trials were successful enough to justify production of a substantial number of rifles for troop trials. This would be designated the No1 MkV rifle, and 20,000 of them were made between 1922 and 1924.

The magazine cutoff was retained in the MkV rifles, as were the volley sights in the initial production - along with an aperture rear sight marked out to 1500 yards. Following concerns about the durability of the sight and its adjustment latch, it was redesigned slightly, and the new version only went out to 1400 yards. On this second variation, the volley sights were omitted.

The new rifles was taken to Bisley and input was sought from both military units and civilian marksmen from the British NRA. The feedback that was received was that the sight was too fragile, its adjustments were too coarse, and the barrel was too light. These changes were implemented in the No1 MkVI rifle which would ultimately be adopted as the N4 MkI; the classic World War 2 version oft he Lee Enfield.