Sturmey Archer 4 speed trigger fault. How to stop it jumping out of gear.

A common fault on the old 4 speeds is the jumping out of First, or Bottom, gear. This is generally caused by wear on the trigger mechanism rather than any fault with the hub, but the strongly sprung First gear exacerbates the problem. Fortunately, it’s an easy fix which can be done without removing the trigger from the handlebars or dismantling.