Prep the glasses a few hours before the party. Tip the egg white and sugar into two separate, shallow bowls. Dip the rims of 10-12 glasses in the egg white, shake slightly to dribble off any excess, or dip them into a glass of Pimms, then dip into the sugar to coat and set aside to dry.
As your guests arrive, mix the pomegranate juice, Pimms, lemon juice and plenty of ice in a jug or two. Top up with ginger beer and pour into the prepared glasses.