‘I am sick of portraits and wish very much to . . . walk off to some sweet Village where I can paint Landskips and enjoy the fag End of Life in quietness & ease,” Thomas Gainsborough grumbled in a much-quoted letter he wrote to a friend.

To learn that for Gainsborough, although painting portraits was his business, painting landscapes was his pleasure was less of a surprise when once home from Compton Verney’s exhibition of Gainsborough’s Landscapes I reached for my National Gallery guidebook to take another look at Mr and Mrs Andrews. This famous double portrait (not at Compton Verney) has the well-heeled couple surrounded by their well-ordered estate. Despite the duo dazzling in their finery, more than half the canvas is given over to the “quietness and ease” of landscape. The Gainsborough’s Landscapes exhibition, previously shown at the Holburne Museum, Bath, is the first in 50 years solely devoted to Gainsborough’s landscapes.

The paintings and drawings on display and the show’s subtitle, Themes and Variations, reveal that the artist had a limited repertory of themes.

He changed his style, however, which developed from early naturalistic landscapes such as River Landscape with a View of a Distant Village, c.1750, a Dutch-inspired Suffolk scene with small foreground figures, to grandiose views dramatically lit with rustic figures centre stage, like Mountainous Landscape with Shepherds and Sheep (‘Romantic Landscape’). Here, the rocks and light have such an air of celestial mystery that I almost expected Joshua to appear and command the sun to stand still, as you would see in a John Martin painting.

Nearly all Gainsborough’s landscapes were imagined. He drew heavily upon the countryside of East Anglia where was born. The creations “of his own Brain” he called them. His recurring themes, wooded landscapes with horses doing this or that, cattle crossing a bridge, cattle at a pool and so on, allow curator Susan Sloman to explore his varying style.

For instance, his move from pencil — apparently not fast enough to get his ideas down — to other media; or how his hand freed up as his career progressed, as in Wooded Landscape with Horses Resting, which skilfully conveys in chalks on grey paper the gentle movements of horses and dappled light, contrasting darker against whiter animals.

To see a well-known work in a new context is always a pleasure. The Watering Place (1774-77), another National Gallery Gainsborough favourite, looks magnificent here, displayed without distractions.

The exhibition can be at Compton Verney, Warwickshire, until June 10. For information go go to the gallery’s website (www.comptonverney.org.uk).