The powerful double portrait of Thomas Wentworth, 1st Earl of Strafford, with Sir Philip Mainwaring, painted by van Dyck in 1639-40, two years before the start of the Civil War, shows (see below) the two politicians working closely together. Weighty matters are at hand. One looks keenly at his colleague, pen poised ready to record; the other, the 1st Earl of Strafford who by this time was the king’s unofficial but most trusted advisor, stares sternly out at us. It’s as though this leading politician is about to make some urgent or ruthless decision, the tension in his face and posture betraying the pressure and responsibility of his role.

Van Dyck (1599-1641), the greatest painter in 17th-century Britain, modelled the painting on a Titian. He had visited Italy some years earlier in the period between his first brief trip to England (1620-21) and his return in 1632 to become the principal painter at the art-loving court of King Charles I. While in Italy he had been inspired by the Italian masters, admiring Titian above all. The Titian in question shows Cardinal Georges d’Armagnac and his Secretary Guillaume Philandrier working together in much the same pose as van Dyck uses 100 years later.

Both paintings are on show though not side-by-side in Tate Britain’s major spring exhibition, Van Dyck and Britain, running until May 17. Tate’s choice of works allows us to see how van Dyck emulated Rubens and Titian, and how, in turn, his innovatory portrait-making influenced those following. There are more than 130 exhibits, from the reign of Charles I onwards right up to the early 20th century, with around 60 by van Dyck. The Tate aims to reveal the Flemish artist’s unique impact on British cultural life in his lifetime, and his continuing visual legacy with portraits by artists such as Sir Joshua Reynolds and John Singer Sargent. The Titian hangs in the first room along with other works from the 1620s to give context to painting in England before van Dyck arrived. Work here also illustrates that despite the brevity of van Dyck’s first visit to England he had immediate impact on artists working at the time. Van Dyck introduced relative informality to portraiture, in pose and dress; flesh began to look like flesh, and emotion appeared. Compare adjacent works by van Dyck and Daniel Mytens, the preceding royal painter: different sitters, identical poses and attributes, but there’s life and energy in van Dyck’s Earl of Arundel that Mytens’s Earl of Pembroke lacks.

The Apotheosis of James I is also on show, highlighting not only that it was “saved for the nation” last year after a big fundraising campaign spearheaded by the Tate, but also the connection between van Dyck and Rubens, his master in Antwerp. Peter Paul Rubens’ preparatory sketch for the ceiling of the Banqueting House, Whitehall is the first Rubens to enter Tate’s Collection, and will be on permanent display.

Antwerp-born Van Dyck was Rubens’s star pupil. He is thought to have been working for Rubens in his workshop by 1615, imitating his style with great skill. The precociously talented boy was the seventh of 12 children of a Flemish silk merchant – his father’s profession surely accounting for van Dyck’s sparkling ability to depict the rich fabrics of the period? It is a huge exhibition, influence, of one form or other, of artist on artist, the king’s, politicians and others’, at its core. It’s visually sumptuous of course, a line-up of dashing royals, courtiers, future Cavaliers, Royalists and Parliamentarians – van Dyck was never an artist of the party, painting as many portraits from one side as the other – all dressed to kill in silks and doublets, displaying armour or ardour or differing degrees of political savvy and influence.

Van Dyck’s portrayals of his many sitters (his output was prodigious), if sometimes over-flatteringly, have shaped our view of the main protagonists of this period of political ferment, the run-up to the British Civil War that resulted in the execution of Charles I.

Highlights include iconic portraits of the king and his family. There is the harmonious family portrait of Charles I and Henrietta Maria and their two eldest children (‘The Greate Peece’) with the hand of the little boy, the future Charles II, on his father’s knee; a five years older Charles II as Prince of Wales, in Armour (child-sized, a hand-down from late uncle Henry); and the magnificent Charles I on Horseback with M. de St Antoine painted in 1633 for the end of the long gallery at St James’s Palace. Charles I handles his gorgeous restive stallion with great ease, a visual metaphor for a king in effortless control of his kingdom. Loans include others from The Royal Collection, eight from the National Trust (none from Oxfordshire properties), one from Blenheim Palace of van Dyck’s mistress Margaret Lemon (posing as Tasso’s Erminia), and the only history painting surviving from van Dyck’s time in England, loaned from Christ Church, Oxford. There are portrait miniatures, engravings, manuscripts, examples of court dress, and a rare view of van Dyck’s preparatory drawings, including a watercolour landscape and studies of the horse in Charles’ equestrian portrait. It is worth going to this exhibition for the great paintings alone. But there’s so much more, to be enjoyed on so many levels, from history to fashion to art, to sheer surface beauty and what’s beyond. And don’t miss in its flamboyant frame what’s thought to be van Dyck’s last self-portrait, the rarely exhibited late portrait (see right) of around 1640, two years before he was to die. The artist paints himself as beginning to age, showing a few grey hairs and signs of strain.

The beautifully illustrated catalogue edited by the exhibition’s curator Karen Hearn, curator of 16th- and 17th-century British Art at Tate, contains contributions from Prof Kevin Sharpe, the exhibition’s historical consultant, and among others, Dr Christopher Brown, director of the Ashmolean Museum.

On until Sunday 17th May. For details see: www.tate.org.uk