Hardham's iconic image of St George on horseback has suffered considerable damage and it's not at all clear what he's fighting. It could be a dragon, but the presence of what looks like a kite shaped shield in the top right hand corner of the composition has persuaded commentators that he's actually riding out against Saracens, as is reported to have happened at the Battle of Antioch in 1098- an event which would have been within living memory- and possibly quite recent memory- at the time the murals were painted.
The fortified city of Antioch occupied a strategic position on the supply route between Europe and the Holy Land. The forces of the First Crusade besieged it in 1097, captured it and were then besieged in their turn by the Turks. On the 28th of June, 1098, the Crusaders staged a breakout. What happened next is described by the contemporary chronicler Peter Tudebode:
"Our bishops, priests, clerks, and monks, clad in sacerdotal garments, marched out of Antioch with the army, carrying crosses in their hands, praying and begging God that He save them and guard and deliver them from all peril and evil. Others stood on the wall by the gate of Antioch, holding sacred crosses in their hands, making the sign of the Cross, and blessing the army. Thus arrayed in battle formation and protected by the sign of the Cross, the crusaders began to march out of Antioch by the gate which is before La Mahomerie.
When Kerbogha saw the Frankish army leave Antioch, one formation following another in well-executed maneuvers, he commanded: “Permit them to come out of Antioch so that we can have a better chance of capturing the main force.” The footmen of Hugh the Great and the Count of Flanders first marched out, and then each rank followed in its order. Following the emergence of the Christian army from the city, Kerbogha became very apprehensive when he saw the great size of the Frankish forces. Consequently, he instructed the emir who was commander of the field operation that if he saw a signal fire rise in the front ranks that he should immediately sound retreat and withdraw Turkish forces, because he would know that they had lost the day. Kerbogha at once little by little began to retire toward the mountain, only to be followed by our army in like moves.
Then the Turks split their forces; one marched toward the sea while the other kept its position. By this move they hoped to trap our army between the two units. Upon observing the Turkish move, our forces formed a seventh line from the troops of Duke Godfrey and the Count of Normandy and made Count Rainardus commander of it. This unit moved against the Turkish contingents coming from the sea. The Turks then engaged them in battle and inflicted heavy casualties with arrows. Our other group drew up ranks between the river and the mountain, a distance of two miles. The second Turkish force began to advance from their position and to surround our men and to wound them by hurling missiles and shooting arrows.
In addition, a vast army riding white horses and flying white banners rode from the mountains. Our forces were, very, bewildered by the sight of this army until they realized that it was Christ's aid, just as the priest, Stephen, had predicted. The leaders of this heavenly host were Saint George, the Blessed Demetrius, and the Blessed Theodore. Now this report is credible because many Christians saw it. The Turkish division flanking the sea became aware of their inability to endure more and kindled a grass fire so that the view of it would precipitate the flight of those in camp. At the sight of the signal fire, the Turks seized and fled with all of their prized possessions and booty.
Our soldiers gradually fought their way to the Turkish tents where the greatest resistance lay. Duke Godfrey, the Count of Flanders, and Hugh the Great rode along the banks of the river, where the Turkish strength was concentrated. Protected by the sign of the Cross, this force was the first to launch a coordinated assault on Kerbogha's troops. After observing this attack, our other line struck the enemy. The Turks and other pagans then yelled out; and our men, appealing to the One and True God, spurred their mounts against the foe. Thus in the name of Jesus Christ and the Holy Sepulchre they engaged in battle, and with God's help the Christians overwhelmed the infidels."