George was 'discovered' by English crusaders in the Holy Land, and became associated with England's crusading nobility, and eventually found favour with the Plantagenet Royal House. Through the devotion of the King and his courtiers, George came to be adopted as the patron saint of the Realm.
Of course, the Kings retained their own Royal Arms, pictured above and below, reminding everyone of their Norman heritage. (Two lions for Normandy, the third added by Richard Cour-de-lion during his reign in the twelfth century)
So today is a very English day, and is often ignored in a very English way too! In defiance of the Anglican dean of Southwark, I'll defy political correctness (or even ecclesiastical correctness) and post the words to a national treasure:
And did those feet in ancient time
Walk upon England's mountain green?
And was the holy Lamb of God
On England's pleasant pastures seen?
And did the countenance divine
Shine forth upon our clouded hills?
And was Jerusalem builded here
Among those dark satanic mills?
Bring me my bow of burning gold!
Bring me my arrows of desire!
Bring me my spear! O clouds, unfold!
Bring me my chariot of fire!
I will not cease from mental fight,
Nor shall my sword sleep in my hand,
Till we have built Jerusalem
In England's green and pleasant land.