William the Conqueror (William I) was the first Norman king of England. In heraldry the lion symbolises bravery, valour, strength, and royalty, because historically it has been regarded as the king of beasts. Lions still appear in the flag and coat of arms of Normandy in France. read more
Richard I (1189–1199) used a single lion rampant, or perhaps two lions affrontés, on his first seal, but later used three lions passant in his 1198 Great Seal of England, and thus established the lasting design of the Royal Arms of England. read more
The short answer is that England wear the three lions on their shirts - as they have done ever since the first international against Scotland in 1872 - because, as representatives of the Football Association, they're simply sporting the logo of the FA. read more