The crusades were a series of military campaigns between 1095 and 1291 against Muslims to reclaim Jerusalem for Christianity, and they occupied it for a while. Keir’s Starmtroopers would probably arrest him.
With the phobia shown by the Starmer regime about displays of the English and Union flags, his police would probably be adverse to this too; but if she had dark skin, they may leave her alone.
Saint George was not a Knight Templar as far as we can tell.
The idea to have your nation flag on a t-shirt is a winner though. Imagine thousands of patriots from any country walking along en masse? Not much any power freaks could do.