IAN COLLINS To see Constable's greatest landscapes we should explore a Tate exhibition and a swathe of surviving East Anglian scenery. Ian Collins follows in a masterly artist's footsteps.

IAN COLLINS

Great artists rarely see the scale of their achievement - and when they do they are likely to be regarded as maniacs. Turner ended his days living under an assumed name, bitterly hoarding the pictures which would not be displayed as he wished until 136 years after his death.

East Anglia's John Constable, equalling Turner as the best British landscape painter of the 19th century, died at the outset of the Victorian era. His towering talent was recognised at once - but chiefly in France, where its influence swelled over ensuing decades until exploding in the colour and drama of French Impressionism.

Suffolk was to be writ even larger in the history of art in the early 1880s when Philip Wilson Steer, fresh from Paris, rushed to Walberswick and to the virtual invention of British Impressionism on our bracing coast.

Now, thanks to a Constable: The Great Landscapes summer blockbuster at Tate Britain, we can trace the story back to its roots in our region and to a short river journey.

For the scenes which made Constable a painter were those revered from childhood in the Stour Valley, especially the sequence of watery views between Dedham Vale and his East Bergholt birthplace. They became magnified - and ever more magnificent - in memory.

By 1819 the artist, finally married to his beloved Maria Bicknell after years of family opposition, and settled in London, was staking his claim to glory, and trying to support his family, by painting colossal images. “I do not consider myself at work without I am before a six-foot canvas,” he wrote.

Over six successive years he showed large-scale “six-footers” at the Royal Academy, each one based on a remembered study of the River Stour and worked out in a full-sized oil sketch which was his most radical innovation.

The triumph of the current Tate show is to have brought all these paintings and sketches together from collections all over the world. The resulting parade of pairings forms an exhilarating sight for East Anglian patriots in particular.

Between The White Horse and The Leaping Horse, via Stratford Mill, The Hay Wain, View of the Stour Near Dedham and The Lock, we can trace the path of greatness to a footpath along the river separating Suffolk and Essex.

For me the experience is infinitely touching - first because Constable never saw these pictures assembled together.

And second because, 180 or more years on, and after ages in which most of England has been transformed beyond all recognition, these panoramas remain little changed. How lucky we are to be able to follow in the artist's footsteps.

Small wonder that today's Stour Valley dwellers have just risen up to defeat a planning application for the vast retail development of a Constable theme park. The artist's real legacy lies in the unaltered landscapes all around them - and within easy striking distance of us.

Oddly enough, the one big change between 1826 and 2006 (aside from the glint and roar of the A12) is that some of the old sweeping vistas of the Stour Valley are now obscured by encroaching trees

But if familiarity does not always bring contempt, it invites easy misunderstandings. Mass reproduction of Constable's greatest pictures - on everything from posters and coasters to tea towels and chocolate box tops - has blurred the truth of the original picture.

East Anglia's vast skies and level scenery suit panoramic canvases, though they have been much diminished in every sense by the marketing of Constable Country imagery. We have looked back in nostalgia to an era of bucolic bliss which never actually existed.

With ongoing fallout from the Napoleonic wars and the enclosure movement, Britain was in a period of extreme social hardship and upheaval when Constable was in his prime - and the countryside was in uproar.

What our native genius painted was not an arcadian paradise, but his delight in an orderly working environment. He admired scenes busy in the rural equivalent of the industrial revolution.

His family owned mills and controlled commercial navigation on the Stour between Sudbury and Mistley - barges being the juggernauts of the late Georgian era. He was able to paint due to profits from the labour he depicted.

But then again almost all of the English landscape is man-made, and one of Constable's great gifts is to remind us that reality can have a greater heroic action and narrative weight than the mythical scenery of earlier English painters.

As he wrote, his best pictures were lit by a love for “the light of nature. The language of the heart is the only one that is universal.”

In this striving for realism he was also paying tribute to his Sudbury-raised mentor Thomas Gainsborough. Truth being stranger than fiction, how astonishing it is that two such giants should have been nurtured in the Stour Valley.

And to understand Constable's revolutionary technique - and his link to modernism - we need to compare the paintings with the full-sized studies which the artist himself regarded as mere working notes.

He made thousands of vital and vibrant smaller oil sketches outdoors in all weathers - with more than a hundred studies of clouds scudding over Hampstead Heath helping the construction of the final, six-footer paintings.

But the full-scale sketches reveal what he was about - the lively, lightning brushstrokes to convey that immediacy of impression which is the key goal of impressionism.

The journey we follow in this exhibition is the artist's quest to make the finished painting as exciting as the preceding sketch. He comes close to a good match in the desolate picture of Hadleigh Castle which followed the death of his wife from TB in 1828 (“a void is made in my heart that can never be filled again in this world”).

And he comes closer still in the visionary spirit of Salisbury Cathedral from the Meadows of 1831, in which an added rainbow also improves on the sketched idea.

Finally, he fully realises his goal with the stupendous canvas, The Opening of Waterloo Bridge.

Having probably witnessed the scene in 1817, Constable strove over the next 15 years before capturing its vivid grandeur.

When he died, suddenly, in 1837, the task he had set himself was really accomplished.

His will did not fail to mention the tenanted Willy Lott's House, which had featured in The Hay Wain and other now-celebrated pictures.

The surprising and even shocking Mr Constable decreed the picturesque hovel an eyesore, and ordered its demolition. Happily his wish for ongoing progress in the Stour Valley was ignored.

Constable: The Great Landscapes is in the Linbury Galleries of Tate Britain (020 7887 8888; www.tate.org.uk) until August 28. Open 10am-5.50pm daily. Admission £10, concessions £8 (entry to the permanent collection remains free)