<p>Joseph Mallord William Turner is arguably Britain's greatest and most mysterious painter, whose range of work encompasses seascape and landscape, immensely powerful oil paintings and intimate watercolours. His friend and colleague C.R. Leslie remembered him thus: 'Turner was short and stout, and had a sturdy, sailor-like walk. He might be taken for the captain of a river steamboat at first glance; but a second would find more in his face than ...