Charles I: King and Collector, Royal Academy ★★★★★

Charles I's glassy-eyed, triumphant stare follows you around the Royal Academy's central gallery. Here, exhibited side by side for the first time in history, are the four most famous portraits of the ill-fated Stuart king. In the two majestic equestrian portraits by Charles' court painter Anthony van Dyck, the king looms larger than life. Measuring only 66 inches, this was no mean feat. Mounted on horse-back, sword in hand, Charles glares down at us, his mortal subjects, with a look of pure authoritative disdain.

Charles I with M. de St Antoine (above) hangs pride of place at the heart of this phenomenal exhibition of more than 140 hand-picked items from Charles I's original art collection. Projecting Charles as a divine, almighty ruler, his power is unquestionable, his magnificence undeniable. With his flowing luscious locks, his polished suit of amour, and blue Order of the Garter sash slung over one shoulder, Charles looks more chivalrous knight than didactic ruler. He looks good. In the most theatrical of royal portraits, Van Dyck depicts Charles as the ultimate good, the next best thing to God.

Anthony van Dyck, Charles I, 1635-6, Royal Collection Trust / © Her Majesty Queen Elizabeth II 2017

Glorious and triumphant, Charles reigns supreme. This formidable royal portrait served as Stuart propaganda. For the first time in British history, Charles exercised his autocratic power through art. As his artistic taste developed, so did his collection. Over a period of nearly twenty-five years, Charles amassed one of the most extraordinary art collections of all time, comprising some 1,500 paintings and 500 sculptures.

Lining the royal blue walls of the Royal Academy are more Italian Baroque and Renaissance masterpieces than you can shake a stick at. Masterpieces by Titian, Veronese and Velazquez, acquired during a trip to seduce the Spanish Infanta in 1623, rub shoulders with glorious works by Rubens, Hans Holbein the Younger and Gentileschi.

Rubens' Peace and War, 1629-30 – presented by the artist himself to Charles to mark his successful peace negotiations with Spain – is one of the most bewitching oils on display. But this is easily topped by the Triumph of Caesar, Mantegna's Renaissance nine-canvas masterpiece depicting the victory procession of Julius Caesar. Read left to right, the story culminates in a scene of chariots, elephants and the crowning of Caesar with a laurel wreath. It's a delicious composition, and a decadent feast for the eyes. A celebration of a self-fashioned authority, the Triumph of Caesar would have struck a chord with the ambitious Stuart king.

Titian (c. 1488/90–1576), Conjugal Allegory (‘The Allegory of Alfonso d’Avalos’), c. 1530–35. Musée du Louvre, Paris, Department of Paintings, inv. 754. Photo © RMN-Grand Palais (musée du Louvre) / Stéphane Maréchalle. Exhibition organised in partnership with Royal Collection Trust

A good number of the works in Charles' collection were acquired in a job lot from the House of Gonzaga in Lombardy. Blighted by disrepute and bankruptcy the aristocratic Italian family sold two thirds of their prestigious art collection to raise funds. For Charles, this was the ultimate jackpot.

But self-involved and unwilling to satisfy the pleas of his uprising people, Charles fell from grace. The first and last British king to be overthrown by revolution, Charles I was executed at the order of parliamentarians in 1649. His collection was sold, for the princely sum of £180,000, and dispersed around the world; much of it snapped up by European royals eager to expand their own collections.

With more than 140 works reunited from Charles' original collection for the first time in 350 years, Charles I: King and Collector is just short of miraculous. Even if you are not a die-hard fan of Baroque and Renaissance paintings, coming face to face with so many oils, marble sculptures, tapestries and paintings by art history's most famous artists is a truly humbling experience.

Be prepared to stand bewitched.