Most of the paintings in our forthcoming exhibition, Masterpieces from Buckingham Palace, are securely dated and attributed; mostly we know which monarch bought them. But what makes them important? What do they still have to offer? Desmond Shawe-Taylor, Surveyor of The Queen’s Pictures, discusses four possible qualities which were valued by the makers of these works and which can still offer an insight into these paintings today: Realism; Use of Materials; Design; Expression. Are we missing something? What do you think makes a masterpiece?