A blind eye.....................................

Admiral Lord Nelson in a great sea battle (the Battle of Copenhagen, 1801) ignored a signal commanding him to disengage with the enemy.  (Admiral Byng's hanging, made famous by Voltaire's remark that "every once in a while you have to hang an admiral to encourage all the others," showed how perilous this decision was.)  Informed of the order from the flagship, Nelson put his telescope to his blind eye (previously lost at the Siege of Calvi).  His decision won the day for the British Navy.  This is a favorite story.  I tell it to kids whenever I can.  Courage, daring, rule-breaking and vindication, all rolled into one.  What could be better!  Sometimes you must put the telescope to your blind eye.

-Sheldon Whitehouse,  On Virtures:  Quotations and Insight to Live a Full, Honorable, and Truly American Life

(Turns out, if you believe Wikipedia, that Byng was shot by firing squad, not hung, for failing "to do his utmost."  Doesn't take away from the author's story though.)