"Did you spill my pint (of mead)?"

Archaeologists working at The Battle of Bannockburn site have discovered new evidence that King Robert and his horse both suffered from pre-traumatic stress disorder. 
This unusual affliction meant that the king and his horse, Trigger, both  had to wear a big blue plastic bag to inhibit over-breathing and possible panic attacks on going into to battle. 
The new evidence therefore suggests that King Robert did not mean to kill Henry De Bohun in single combat. 
It was actually Henry's brother, Clint, he'd meant to kill for spilling the king's pint of mead the night before in The Bannockburn Arms, but Robert blindly twatted the wrong knight with his axe.
It is thought that the renovated statue of the king has been re-designed to reflect our update in historical understanding.