The National Gallery complex on Edinburgh’s Mound is the capital’s top free visitor attraction. Walk through Playfair’s stripped classical, red sandstone portico, bear left and there, occupying an entire wall in a gallery of monster canvases each doing the same, you will come face to face with £50 million worth of Titian. Saved for the nation, by the nation, Diana and her nymphs surprised by Actaeon was painted in about 1556, quite probably at the same time as the Archbishop of Canterbury was being burned at the stake for treason.