Brian Sewell is the often acerbic and always fearless art critic on London’s Evening Standard. In his scholarly and amusing series Brian Sewell’s Grand Tour (2006, now available on DVD) when commenting on Gianlorenzo Bernini’s Fountain of the Four Rivers in the Piazza Navona at Rome, he remarks that at the time it was constructed in 1651, Australia had not yet been discovered. However, by the time of the death of the Italian master engraver and etcher Giovanni Battista Piranesi (1720–78), this country had not only been discovered, but had been taken possession of for the British Crown by Captain…