He fought in the invasion of Sicily in July 1943 and was awarded a bar to his DSO for the brigade's part in the Battle of Centuripe in August. The brigade then took part in the invasion of Italy in September. Howlett was promoted to lieutenant colonel on 24 November 1943, still acting as brigadier. 36th Brigade was engaged with the enemy along the River Sangro at the time and Howlett was killed by German artillery fire on 29 November at Santa Maria Imbaro. He had gone forward on horseback to visit his forward troops and was caught in the artillery fire. He was 44 and had been due to be promoted to major-general to command a division in the Normandy landings. Howlett is buried in the Sangro River War Cemetery. He was posthumously mentioned in dispatches.