Saint George's Day--April 23 (Same as Shakespeare's birthday and deathday, many argue.)
The Patron Saint of England
From Shakespeare's Henry V (the rallying cry before Harfleur): "Cry God for Harry, England and St. George!"
Images from the early modern period
From the 20th Century--Salvadore Dali's representation
St. George's Shield became the flag of England (it was incorporated into the Union Jack). It has since become a rallying point for some extremists who oppose immigration and the presence of foreigners in the UK.