It's purely an accident.
Her hair - caught in his rank pin when they both lean forward to look at her notes, being pulled sharply when he leans back.
It's completely unexpected.
Her moan - low and throaty, eyes fluttering closed, tongue wetting lips.
It's everything he wanted.
Her skirt pushed up, his hand between her legs, two fingers being thrust quickly and rhythmically into her welcoming body.
It's sudden.
Her climax - a breathless gasp, shuddering body, gentle murmur of his name.
It's over.
She untangles her hair and returns her attention to the notes before them.