赤毛のアン2章11

Had he looked he could hardly have failed to notice
the tense rigidity and expectation of her attitude
and expression.

never fail to:必ず～する
tense:張り詰めた
rigidity:硬さ
expression:表情

見ていたら、その子の態度や表情から期待と緊張がきっと
見て取れていただろう。

Had he looked = If he had looked の仮定法