Bodyline bowling was developed in an innovative way. In reviewing film of unbeatable Bradman at the crease, the England captain saw him flinching when a ball passed close to his head. Exploiting that weakness turned out to be the only way to defeat him.
It’s not that Keir flinches, but the right sort of attack gives us a glimpse of his weakness. Students of the PM will have their own description of what that weakness is but, in this reading, when facing a certain sort of delivery, he betrays something short of panic but very far from ease.
