 Agamemnon 's first target service took place before her modifications were completed . On 19 March 1921 , she was exposed to a cloud of poisonous gas to determine the effect of gas on a battleship . It was found that gas could penetrate the ship via her various openings , but the ship had not been sealed against gas before the trial and no accurate results applicable to a commissioned battleship could be obtained . On 21 September , she was subjected to machine @-@ gun fire by strafing aircraft . These trials showed that such strafing could harass a battleship , but could not impair her fighting or steaming capabilities , and helped to determine protection for bridge personnel . 
