Complex sentence: He executed at least 400 people, about half of them war criminals including William Joyce, one of the men dubbed "Lord Haw-Haw", and John Amery, whom he considered the bravest man he had ever hanged.
Split into simpler sentences: He executed at least 400 people, about half of them war criminals. Among these were William Joyce, one of the men dubbed "Lord Haw-Haw", and John Amery, whom Pierrepoint considered the bravest man he had ever hanged.