Henri III was a King of France in the 16th century. During his reign in 1578 he began the construction of Le Pont Neuf, a bridge in Paris across the river Seine to an island in the river. When the First Doctor and Steven Taylor arrived in France in 1572, the two used the absence of this bridge and the Doctor's knowledge that Henri III initiated its construction in 1578 to estimate what year they had arrived in. (PROSE: The Massacre)