Turner:simply the best?

The revered painter conjured scenes of gods and legends, but his work came to represent the complex soul of Britain like no other artist

- Jonathan Jones

He never crossed the Atlantic. Never sailed the Aegean. A cross-channel ferry was enough for Joseph Mallord William Turner to understand the might and majesty of the sea. His 1803 painting Calais Pier records his feelings on his first arrival in France as foaming green mountains of waves look as if they're about to sweep away the frail wooden jetty where passengers from England are expected to disembark.

He is fascinated and appalled by the water, so solid in its power but always shifting, dissolving, sheering away.

If JMW Turner, born 250 years ago this month, is Britain's greatest artist - and he is - it is partly because he is so intensely aware of a defining fact about his country: it's an island. For Turner, Britain is bordered by death, terror and adventure. Just one step from shore takes you into a world of peril. In the Iveagh Seapiece, fishers are hauling up their boats on a soaking beach while a wave like a wall surges towards them. One fishing boat is still out on the wild waters, so near to shore yet so far from safety.

Island artist though he is, Turner's imagination is the opposite of insular. It takes in lost civilisations and ancient myths, mountains he crossed and seas he never did. The wars that started with the French Revolution in 1789 had imprisoned Britain behind the Royal Navy's "wooden walls".

When a short-lived peace broke out, the young landscape artist took his chance to travel, seeing a wine festival in Mâcon, gazing in awe at Mont Blanc - to judge from paintings he showed the next year. Before he ever saw the continent, he painted legendary Italy. All his life, he would keep up Europhile painterly pilgrimages to Venice and Rome, Heidelberg and the Saint Gotthard Pass.

Turner was born in London, on 23 April 1775, in a Britain that seemed a much bigger place than it does now. Every distance was vaster, every road felt longer. It took several days to get from London to Chester, Newcastle or Exeter.