Frank Auerbach was evacuated from Berlin to England in 1939, as the Nazis’ persecution of the Jews spiralled into genocide. He was seven years old at the time. He was sent to boarding school, first in Kent and then on the Welsh Borders. He was still an evacuee schoolboy when he discovered that both his parents had lost their lives in a concentration camp. After the war was over, Auerbach settled in London. He studied painting first at the Hampstead Garden Suburb Institute and then at the Borough Polytechnic, where his teachers included the inspirational David Bomberg. Bomberg had been a leading light of the Vorticist movement in the years before the First World War, but by the late 1940s he had abandoned the juddering abstractions of his youth to work in a richly expressive figurative style. Bomberg painted the landscapes of Palestine and Spain and the cityscapes of war-torn London, seeking not exact representational truth but something more nebulous and personal – “the spirit in the mass” was his mantra.

The young Auerbach was deeply impressed, both by Bomberg’s work and by his teaching. After completing his education at St Martin’s School of Art and then the Royal College, he embarked on his own career as an artist. By 1954, he had his own studio in Camden Town. He has been there ever since, painting the city, painting portraits of his friends, painting the gentle arc of Primrose Hill against the sullen London sky, with a fiercely productive energy that has now lasted more than half a century. At the age of seventy eight he is still going strong. At his best, he is an artist of immense power and seriousness, heir not only to his first mentor, Bomberg, but also to John Constable, that passionate, stubborn, uncompromisingly radical painter of the English landscape, for whom painting was “but another word for feeling”. Auerbach is one of the few modern British painters to have manifestly grasped the wrenching significance of Constable’s work, especially his desolate later paintings, with their raging screeds of mark-making – fields of paint ploughed through with sorrow, rage and regret.

Auerbach’s own art has always been built on the conviction that paint should be treated as an expressive material as well as a medium of representation. His pictures have often been densely worked, so thick with accreted layers of underpainting that they seem to hover somewhere between two-dimensional images and three-dimensional objects. This was particularly true of the paintings that he created during the first ten years of his career, from 1952 to 1962. Long since dispersed among different private collections and public museums as far afield as Australia, they have now been reunited in a compelling exhibition at the Courtauld Galleries. Collectively entitled “London Building Sites”, their literal subject is the post-war rebuilding of the city in which Auerbach had chosen to live and work. Several were inspired by the construction of the Shell Building, near the Festival Hall. Others recall building sites in Portobello, Oxford Street and Victoria. All are dense, pitted, thickly impasted, looking at first sight as though they might have been formed from the clay, mud and grime scraped from a construction worker’s boot. They work not only on the eye but, in the words of Auerbach’s slightly older contemporary, Francis Bacon, on “the nervous system” of the viewer. Looking at them is like dabbling in mud, like being touched by primordial slime. Several are so heavily laden with pigment that they seem at risk of sliding off the canvas and finishing in a mess on the gallery floor.

The catalogue to the Courtauld’s exhibition includes some of the artist’s own reminiscences about London in the 1950s and early 1960s:

“It was pitted with bomb sites and of course the bomb sites gradually turned into building sites because people were rebuilding what had been destroyed. And there was ... a sense of survivors scurrying among a ruined city ... A city fully functional is to me a somewhat formally boring collection of cubic rectilinear shapes, but London after the War was a marvellous landscape with precipice and mountain and crags, full of drama ... in Paris, you’d be haunted a little bit if you started trying to paint Notre Dame or a view of the Seine by the fact that other people had painted it before, but the London I knew and saw hadn’t really been painted ... it was a new phenomenon.”

That last remark is not strictly true, since Auerbach’s former teacher Bomberg had himself drawn and painted views of bomb-damaged London. In fact there is a distinct kinship between a drawing of Bomberg’s such as Evening in the City of London (in the Ashmolean Museum) and Auerbach’s slightly later drawings for the “Building Site” series, which are being exhibited at the Courtauld alongside the paintings themselves – a shared fondness for vertiginous perspectives and slashing, shorthand abbreviations of architecture. But in the act of transforming his drawings into the finished oils, Auerbach did indeed chart entirely new territory.

The “Building Site” pictures stand confirmed, by this showing, as among the most solemn and most moving pictures created anywhere in Europe during the post-war years. They have a brutal, bruised monumentality about them. Some are nocturnes but their dense blackness communicates a sense of atrocity as well as conjuring up night. The darkest of all, Shell Building Site: Workmen under Hungerford Bridge, seems to evoke things twisted or burned beyond recognition. Even those pictures brighter in colour, lifted by touches of clay red or the ochre of earth that has just been turned, are shot through with morbidity.

Concealed deep within these images there are signs of structures taking shape, beams and girders, wedges of vestigial architecture, hints of crane and hoist. A literary interpretation might easily misidentify them as images of optimism, symbols of London as a phoenix rising from the ashes of wartime adversity. But Auerbach’s thick layers  of paint are too heavy with melancholy, too fraught with implications of all that lies buried and lost beneath the surface, for that to be true. The “Building Sites” are more understated than the pictures being painted at exactly the same time by Francis Bacon – there are no screaming Popes, no limbless children here – but they too offer bitter commentary on a cruel and absurd world. They are images of a city scarred by war, painted by a man whose family had been murdered in the same conflict. The world they depict may be rebuilt, but it will be rebuilt on top of freshly dug graves.