We all think we know John Constable, but his current role as poster boy for the British heritage industry obscures the fact that in his lifetime he was seen as a radical realist who often shocked his contemporaries by wanting to pin down the rude truth of the ordinary world around him.

He was the first artist to paint entire large canvases outdoors, declaring that, “we see nothing until we understand it,” and when a critic dismissed his vast painting of The Opening of Waterloo Bridge as unfinished, he snarled, “my art flatters nobody by imitation,  it courts nobody by smoothness, tickles nobody by petiteness …there is no finish in nature.”

To this end, although he was mainly based in London, Constable doggedly returned to and studied the East Anglian landscape of his childhood, zeroing-in on its minute and mundane details stating that, “the sound of water escaping from mill dams etc., willows, old rotten planks, slimy posts, and brickwork, I love such things… these scenes made me a painter and I am grateful.”

But now a major exhibition at the V&A reveals an equally important but largely overlooked aspect of England’s best loved artist by providing fascinating and comprehensive evidence that it was not only Constable’s “careless boyhood” on the banks of the River Stour that fed and shaped his vision but also his scrutiny of the art of others. For the first time Constable: The Making of a Master examines his work in conjunction with the major 17th century painters of classical landscape such as Jacob Ruisdael, Peter Paul Rubens and Claude Lorrain as well as leading British artists of the day, including Thomas Gainsborough, John Martin, Thomas Girtin and John Robert Cozens, all of whose work Constable assiduously studied, copied and often owned; and with whom he had as rich and complex a relationship as he did with the landscape around his father’s mills in Dedham and Flatford.

Thanks to the art owned by his mentor, the patron and amateur painter Sir George Beaumont, and to his studies at the Royal Academy of Art, Constable had direct access to a wide range of art from the past and present. We see that from early on he made painstakingly exact copies of works by Ruisdael, Claude and Titian firstly as a means to learn from their compositions and execution and later as an act of homage - to “hold commune” as he put it - with his art historical heroes. He also built up his own considerable collection of artworks, including 5000 etchings – amongst them works by Durer, Rembrandt and Claude – which acted as an enduringly valuable recourse.  His friend and biographer Charles Leslie remembers that at the end of his life Constable’s attic bedroom in Charlotte Street was lined with his collection of engravings and “his feet nearly touched a print of the beautiful moonlight by Rubens” and a version of this print, along with many of his other favourite artworks have been brought together at the V&A for the first time.

There’s also the revealing juxtaposition of the original Rubens Landscape by Moonlight – from which his bedside print was taken and which Constable knew well from the collection of Joshua Reynolds – with the Moonlight Landscape with Hadleigh Church painted when Constable was just 20 and which clearly owes as much to Rubens as to the Suffolk landscape; and throughout this exhibition repeatedly confirms how culture as much as nature informed Constable’s art.

Even his most famous Suffolk scenes combine motifs, devices and compositional elements from his art heroes with the directly-observed landscapes he saw around him. Whether it is The Cornfield fusing a vista of Dedham Vale with the compositional structure of  Claude’s Landscape with Hagar and the Angel; his epic The Opening Waterloo Bridge finding him looking hard at Canaletto’s Thames paintings, or the No. 1 Constable classic, The Hay Wain, which is here revealed to be directly inspired by a very particular Rubens landscape, A View of Het Steen in the Early Morning, while at the same time presenting an utterly recognisable view of the River Stour near Flatford.

Yet the strength of this exhibition is the way in which it manages to highlight these important and hitherto little known art historical influences whilst avoiding dry, academic reference-spotting. For as well as introducing Constable’s wide and deep engagement with other artists, Constable: The Making of a Master also brings together the multitude of directly-observed studies that simultaneously accompanied and fed into his paintings.

It is a real treat to be able to look at these stunning, on-the-spot sketches of skies, plants and precisely-rendered items of farm machinery that were an equally crucial component in shaping his vision; with another major highlight being the rare opportunity to see the full-sized and freely-executed (and often to modern eyes more powerful) preparatory “sketches” for The Leaping Horse and The Haywain, twinned with the “finished” paintings.

As a result of the V&A’s terrific show we see that  much of Constable’s brilliance and his ability to speak to us through the centuries lies in the fact that he was able to state, “I see Gainsborough in every hedge and hollow tree” while also declaring, “I know dock leaves pretty well, but I should not attempt to introduce them into a picture without having them before me” and be able to fuse these two strands of inspiration into a rich and complex language that was – and is – utterly his own.

Constable: The Making of a Master (supported by the Friends of the V&A with thanks to Windsor & Newton), until January 11