On December 18 Sciré released the manned torpedoes 1.3 miles from Alexandria commercial harbor, and they entered the harbor when the British opened the boom defence to let three of their destroyers pass. After many difficulties, de la Penne and his crewmate Emilio Bianchi successfully attached a limpet mine under HMS Valiant, but had to surface as they attempted to leave and were captured. They refused to answer when questioned and were detained in a compartment aboard Valiant.