The Howell was designed during World War I with the intention of providing standard infantry troops with increased firepower, which would have been useful, at least in theory, in the close-quarters combat of trench warfare. However, it was turned down by the British Army on account of its lack of resiliency against the harsh conditions of the war. The few examples that were built were made by Birmingham Small Arms.
When World War II broke out, there was some renewed interest in the Howell rifle. It was considered by the British Ordnance Board as a potential anti-aircraft weapon for Home Guard units, although it was ultimately never actually issued.
The Howell was a Lee-Enfield No.1 Mk.III with an external gas tube fitted on the right side of the weapon. The bolt handle is cut off but is retained on the gun, and is surrounded by a curved cam connected to the gas tube. When the gun is fired, the gas piston pushes the cam, rotating the bolt handle and pushing it open, before a spring pulls the bolt back in.
The sights were offset, similarly to the Bren gun, although the original Lee-Enfield sights were not removed. The trigger is modified to incorporate a new disconnector safety. It could use 20-round extended magazines or standard 10-round SMLE magazines.
To prevent the shooter's hand from interfering with the action, a pistol grip is attached to the stock and surrounded by a large hand guard that prevents the hand from moving too far. An extra metal tab prevents the shooter's face from moving too close to the action.