On his appointment as Principal Painter to Charles I in 1632, the Flemish artist Van Dyck - Rubens's most gifted follower - was required to specialise in portraiture. This is one of the chief paintings to result from his appointment, which revolutionised British painting and provided us with the enduring image of the Stuart court. With great fluency Van Dyck here portrays Charles I on horseback on an unprecedented scale, as ruler, warrior and knight, in the long tradition of antique and Renaissance equestrian monuments. The prominent display of the crowned royal arms and the triumphal arch framing the armed King reinforce his image as ruler of Great Britain, while the King's refined features, loose hair and the sash of the Order of the Garter worn over his armour convey the impression of a chivalrous knight. Van Dyck may have designed the painting for its first position at the end of the Gallery at St James's Palace, where its theatrical effect impressed visitors. Both artist and patron admired and collected works by Titian, but a more direct influence was Rubens's 1603 portrait of the Duke of Lerma (Madrid, Prado) which Charles I would have seen on his visit to Spain as Prince of Wales in 1623.

Skilled horsemanship was regarded as the epitome of virtu and here Pierre Antoine Bourdin, Seigneur de St Antoine, a master in the art of horsemanship, carries the King's helmet. Sent by Henry IV of France to James I with a present of six horses for Henry, Prince of Wales, in 1603, he remained in the service of the Prince and later of Charles I, as riding master and equerry. He looks up at the King, whose poise stabilises a scene filled with baroque movement.

Van Dyck went on to paint two other major portraits of the King with a horse: Charles I on horseback, c.1636-8 (London, National Gallery) and Le Roi à la Chasse, c.1635 (Paris, Louvre). The present painting hung at Windsor Castle for much of the nineteenth century; it is recorded in the Queen's Presence Chamber and the Queen's Gallery (also known as the Van Dyck Room).

Catalogue entry adapted from Royal Treasures, A Golden Jubilee Celebration, London 2002