Lieutenant Commander Sean Ramsey is a former member of the Royal Navy who served as the leader of the Immunes and was the self-appointed commander of the former Royal Navy HMS Achilles. In S02E05, Ramsey tells Niels Sørensen that he was submarine's coxswain, a position that is usually held by a senior chief petty officer, prior to the pandemic killing the rest of the crew. He is presumably dead after HMS Achilles sank with him aboard. He is portrayed by Brían F. O'Byrne.
