Auction introduction: Leading the Old Masters Evening Sale on 1 July is Canaletto’s breathtaking Venice, the Return of the Bucintoro on Ascension Day, from the early 1730s, a sublime masterpiece once owned by Britain’s first Prime Minister, Robert Walpole, and displayed at 10 Downing Street. The sale also showcases two rare and exceptional Dutch still lifes, A pair of still lifes of flowers and fruit by Jan van Huysum, and A pronk still life with luxurious objects and exotic fruits by Jan Davidsz. de Heem.