"Yes. It's on, don't worry - flick it up with your thumb to switch it off. When it fires it'll kick back against your hand; don't fight it, just absorb it."

She stays where she is for the moment - and leaves her hands where they are, too, since Martin doesn't seem inclined to object.

"Use your left hand to steady it, look along your right arm to line it up, flick the catch up, steady... and pull the trigger."