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.
From Inquiries into the Origin and Processes of the Science of Heraldry in England by James Dalloway, p30
Two versions of the Great Seal of King Richard I. The one on the left is from 1189, the one on the right from 1195. The three lions of England are just barely visible on the latter.
It was in the time of Richard I that heraldry assumed more of the fixed character it now bears. That monarch appears on his great seal of the date of 1189, with a shield containing two lions combatant; but in his second great seal (1185) three lions passant occur, as they have ever since been used by his successors.
From The Curiosities of Heraldry by M. A. Lower