The white cross, saltire or St Andrews Cross is of course the national flag of Scotland.
It`s highly unlikely that it would have been worn as a badge and perhaps not even flown as a flag in battle until the XVc.
It did however appear in Scottish seals going back to the XIIc.
Like the Carrick heraldry which probably wouldn't have been borne so prominently by the Man at Arms in ether surcoat or shield it's inclusion by Glenn works really well.
What is achieved in a single figure is national identity and allegiance to a particular family.
Using the Bannockburn reference we have a date and consequently a name for the then Earl of Carrick.
Edward Bruce, an interesting but often ignored member of the family.
Basically by picking up on a few visual references a whole story emerges. Is it historically accurate?..... in my view absolutely yss. Glenn's taken contemporary and relevant references and used them in a visually informative way to great effect