Arms of the Duke of Aquitaine

From The Blazon of Gentrie by Sir John Ferne (1586) p218

Blazon: Gules a lion passant guardant or

Ferne repeats the common trope that the arms of England originated from combining the arms of Normandy with those of Aquitaine after Richard I, heir of Eleanor of Aquitaine, took the throne. While this is difficult to prove, Richard I certainly used the three lions passant guardant during his lifetime, as evidenced by his Great Seal.