Waldemar Januszczak hails the achievements of William Dobson, court painter to Charles I, and the first great national portrait painter

When John Aubrey, the gossipy Baroque biographer, declared that William Dobson (1611-1646) was "the most excellent painter that England hath yet bred", he was on fairly safe ground. Aubrey was writing at the end of the 17th century. Hogarth had not yet been born; neither had Gainsborough, Turner or Constable. Among Dobson's predecessors, there were no obvious rivals, either. Nicholas Hilliard, who did such scintillating work for Elizabeth I and James I, was hugely gifted, but he was a miniaturist. Before Dobson, the big steps in British portraiture had been taken by foreigners.

Holbein, who brought his genius to the court of Henry VIII, was from Switzerland. Daniel Mytens was Dutch. Then, early in Charles I's reign, the incomparable Van Dyck arrived from Antwerp. Dobson, however, was born in London and lived there all his life, except for the momentous sojourn in Oxford that we'll be coming to. He was of particularly English stock, and it gave his art a particularly English flavour. You can see it immediately in the rare self-portrait that has arrived at Bonhams to be offered in July's Old Masters Sale. The direct pose. The expectant face. The gauche confidence of the thick splodges of impasto. These are new qualities in art: English qualities. And because this is an early self-portrait, we can see them here in such a fresh and fledgling form.

But it wasn't only the type and depth of his talent that made Dobson so "excellent". Artistic greatness is dependent on the skill in your fingers, yes, but it also depends on your circumstances: the times you live in. And it is here that he scores astonishingly highly on the excellence-meter. When the Fates decided to drop him where they did – plumb in the middle of the English Civil War – they put him in the witness box of the most dramatic epoch in Britain's history; an epoch which concluded with the execution of the king and the triumph of Oliver Cromwell. For the first truly characteristically English painter to be there to witness the momentous national unfoldings was good fortune on a divine scale.

There are fewer than a dozen contemporary documents that refer directly to Dobson. His life is largely a mystery. It is said that he trained under the stiff court portraitist, Robert Peake, and that he also worked with Abraham van der Doort, who'd been given the task of cataloguing the superb collection of art built up
by Charles I.

When it comes to art, Britain has not been blessed with especially enlightened monarchs. The exception was Charles I. Under him, Britain became nothing less than the greatest collecting nation in Europe. The range and depth of his acquisitions, especially in the field of Venetian art – Titian, Veronese, Tintoretto – were spectacular.

Unfortunately, England did not deem it right for the monarch to spend huge amounts of national cash on the popish outpourings of dead Italians. Soon after Charles was beheaded, Cromwell began selling off the Carolingian collection. You know all those great Titians in the Prado in Madrid? They used to belong to us.

But we're rushing ahead of ourselves. While William Dobson was acquiring his art education under Abraham van der Doort in the 1630s, the royal palaces were still packed with glorious examples of Renaissance creativity. Dobson thus had access to the most educative stash of art that any native talent had previously encountered. The Bonhams self-portrait must have been painted about now; when he was in his early twenties would be my guess.

Two other self-portraits survive: an oval one which belongs to the Earl of Jersey and hangs in Osterley Park; and the great triple portrait with celebrated composer and musician Nicholas Lanier and leading courtier Charles Cotterell in Alnwick Castle. In both of them Dobson is substantially older and has lost the boyish eagerness that is such an appealing feature of the Bonhams portrait.

At some point, he was drawn into the orbit of the king's resident genius, Van Dyck – perhaps as a pupil – and his paintwork grew smoother and more elegant. Here, he is still displaying the heady, unreconstructed influence of all those boldly brushed Titians and Tintorettos that Charles was so keen to collect.

The Bonhams portrait used to hang in Howsham Hall in Yorkshire, where it belonged to the Strickland family, and was joined by the portrait of Dobson's wife, Judith, which is now in Tate Britain. She, too, is an excellently and unmistakably English presence: buxom, flirty, direct: the artist's wife as tavern wench. Although the same size, the two portraits do not form an obvious pair. Dobson's is looser and more frontal. Judith, who remained in Oxford after the Civil War and became a friend of John Aubrey's (who was instrumental in selling off the art by her husband that remained in her possession) probably kept them together. That was how they were sold on.

We don't know when Dobson entered the service of the king. There must have been some paperwork on the subject but, like so much documentation of the times, it was destroyed in the Civil War that broke out between Charles and the Puritans in 1642. This is the epoch in which the Fates intervened so tellingly. Van Dyck, the king's official portraitist, died suddenly in 1641, perhaps from the pox, and a vacancy arose at court for a royal painter. Dobson's appointment as the Sarjeant Painter to the King must have come soon after Van Dyck's death. By late 1642 he was ensconced in the exiled court in Oxford and painting some of the finest and most distinctive portraits in British art.

His first Oxford pictures are a far cry from the modest head and shoulders of his earliest selfie. In the superbly showy likeness of John, 1st Baron Byron, now in Tabley House, he captures perfectly the notorious arrogance of 'the cruel dog of the Royalists', with his war scars on his cheek and his backcloth of huge Solomonic columns.

The chunky format Dobson employed in Oxford made his art feel more foursquare and honest than Van Dyck's flattering elongations. Where Van Dyck made his sitters thinner and taller, Dobson makes them fatter and broader. In Van Dyck's portrait of the courtly mover and shaker Endymion Porter, he looks every inch the English gentleman. By the time Dobson paints him in Oxford, red-cheeked and portly, he could be the village butcher.

What few records remain of the court's exile in Oxford tell us nothing of Dobson's activities. At some point he rented rooms in St John's College, where he was joined by his 'man', Hesketh (the only mention of Dobson having a pupil). This was Father Jerome Hesketh, a Catholic 'hedge priest' and a singularly bad painter who later had a remarkable career as a travelling cleric, touring the Catholic houses of Lancashire, performing secret masses and painting portraits as his cover.

Dobson's own Catholic leanings can only be surmised. Judith's family was buried in the Catholic church in Oxford. And St John's was a notoriously Catholic college. It is also likely that Dobson's most surprising painting – his Caravaggesque copy of Matthias Stomer's Beheading of St John the Baptist in the Walker Art Gallery in Liverpool – was painted for and at St John's.

His Oxford art is remarkable also for the baroque complexity of its symbolism. A typical Dobson will be packed with classical reliefs and bits of statuary. Critics sometimes dismiss these classical extras as clunky and simplistic, but they were actually highly inventive in their symbolic ambition. For instance, in the marvellous double portrait of a young and an old man in the Courtauld Gallery, the only clue to the identities of the sitters – the poets John Taylor and Sir John Denham – is the classical fountain at the back on which Cupid rides a sea-monster to show that love conquers all. The two were very different men. Taylor was humble and self-taught; Denham was rich and privileged. But both wrote about the Thames, which Dobson shows winding quietly behind them, and in Oxford the old poet and the young were united in their love for the king.

The Oxford years turned out to be the high point of Dobson's career. Indeed, they were pretty much all that it consisted of. As Royalist fortunes declined in the Civil War, supplies of paint, food and sitters began to run out. By 1646, the war lost, Dobson was back in London, impoverished and living in an alms house, according to some reports. By the end of the year he was dead. As a career it was tragically short, but its achievements, and its moment, were huge.

Waldemar Januszczak is the art critic for The Sunday Times.

Lisa Greaves, Director of Old Master Paintings, talks about Self-Portrait by William Dobson at bonhams.com/video/21675