I can think of better pubs than the Malt Shovel, and better pints than Deuchars - but if you're offering, I wouldn't turn either of them down.
(Yes, have a pint is the obvious solution to a mere hour of freedom. But how well do you know Edinburgh? Take a camera and have a walk? Go to the National Gallery/RSA, or to the Gallery of Modern Art? Carefully avoid the street theatre that'll be infesting the place at the moment? Pick something from the Fringe with the sole criterion that its timing fits yours?)