Boris Attends Ken's Stag Do

Boris attends Ken's stag do. After many drinks, Boris takes to the dance floor in an attempt to impress a girl. When Ken hears a Bee Gees tune being played, he runs to the dance floor in excitement. Boris sees Ken running towards him with a fist in the air and mistakenly believes that Ken is about to strike him. Boris punches Ken in the face, knocking him to the floor. Boris is charged with battery and wishes to plead self-defence. Which of the following statements is most likely to be true?

A) Boris will be able to rely on the defence of self-defence
B) Boris will not be able to rely on self-defence because he struck Ken first
C) Boris will not be able to rely on self-defence because mistake precludes the defence
D) Boris will not be able to rely on self-defence because his mistake was due to intoxication