Home porn puts gas in the empty tank of a faltering relationship and gives couples a new lease of sexual life. It’s fun, too. Home porn is easy to make. In fact it’s never been easier to shoot, light and edit your own erotic movie and show it life-size on the bedroom wall while you re-enact every kiss, lick, suck and manoeuvre. Like shadows. Or avatars. Or twins separated in some fantastical myth.