Stand in front of Hans Holbein's 1533 masterpiece The Ambassadors and you see wealth, cutting-edge science, and confident diplomacy. Step to the side and a stretched smear across the floor resolves into a human skull. This episode is a forensic investigation of a single oak panel painted as Elizabeth I was born, the Reformation was fracturing Europe, and Henry VIII was breaking with Rome to marry Anne Boleyn.

We identify the two men, French ambassador Jean de Dinteville, aged 29, and Georges de Selve, a 25-year-old bishop on a secret visit hidden from French officials, standing on a replica of the Westminster Abbey coronation pavement. Then we work down the two-tiered table: a celestial globe set to Rome's latitude, a sundial showing two different times, a shepherd's dial casting an impossible curved shadow, an upside-down terrestrial globe ...