Giambattista Tiepolo was the last of the great Venetian decorators, the purest exponent of the Italian Rococo, and arguably the greatest painter of the 18th century. Tiepolo was equally prized as a draftsman: his powers of invention were boundless and his facility without equal. His enormous output of frescoes and altarpieces was partly due to his practice (like Rubens before him) of painting small 'modelli' which, when approved by the client, could...