Last November, the famed British art dealer, Leslie Waddington, passed away, leaving behind a monumental collection of modern and contemporary masterpieces. Christie’s has just announced that it will offer 200 works from Waddington’s illustrious collection this October in London. Among the sale’s most talked about lots are a 1950s painting by Jean Dubuffet, a rare, wall-mounted mobile by Alexander Calder, and an abstract work by Agnes Martin.