It was cold in London on the morning of January 30, 1649—the day King Charles I was scheduled to be beheaded on a scaffold in front of the Palace of Whitehall, following a conviction for high treason during the English Civil War. Dressing before before sunrise, the king reportedly donned an elaborately patterned “sky-coloured satten wastecoat” beneath his black garb. He didn’t want to shiver in the winter air, it’s been said. “He didn’t want people to think that he was frightened,” says Meriel Jeater, a curator at the Museum…