Until this time the British, at RAF insistence, continued their World War I use of machine guns, and introduced twin MG mountings for AAAD. The army was forbidden from considering anything larger than .50-inch. However, in 1935 their trials showed that the minimum effective round was an impact fused 2 lb HE shell. The following year they decided to adopt the Bofors 40 mm and a twin barrel Vickers 2-pdr (40 mm) on a modified naval mount. The air-cooled Bofors was vastly superior for land use, being much lighter than the water-cooled pom-pom, and UK production of the Bofors 40 mm was licensed. The Predictor AA No 3, as the Kerrison Predictor was officially known, was introduced with it.