When in command of a section of Whippet Light Tanks in action this officer displayed most conspicuous bravery and initiative in getting out of his own tank and crossing open ground under heavy shell and machine-gun fire to rescue the crew of another Whippet of his section which had side-slipped into a large shell-hole, overturned and taken fire. The door of the Tank having become jammed against the side of the shell-hole, Lt Sewell, by his own unaided efforts, dug away at the entrance to the door and released the crew. In doing so he undoubtedly saved the lives of the officer and men inside the Tank, as they could not have got out without his assistance. After having extricated the crew, seeing one of his own crew lying wounded behind his Tank, he again dashed across the open ground to his assistance. He was again hit, fatally, in the act of dressing his wounded driver. During the whole of this period he was within full view and short range of the enemy machine guns and rifle-pits, and throughout, by his prompt and heroic action, showed an utter disregard for his own personal safety.