Mondrian | Nicholson - In Parallel (The Courtauld)

A record of a beautiful artistic friendship.

Mondrian | Nicholson - In Parallel

The Courtauld Gallery, London WC2

These days, you don't really associate London's Belsize Park with avant-garde visual arts. Washed-up Britpop stars and a nice branch of Daunt Books, yes, but not the epicentre of the international art scene. But for a while, in the 1930s, leafy NW3 was the Dalston of its day, with a colony of experimental artists that included Henry Moore, Barbara Hepworth and Ben Nich­olson. In 1938, they were joined for two years by a pioneer of abstract geometric art, the Dutch painter Piet Mondrian.

The Courtauld's exquisite exhibition is a record of the period Mondrian and Nicholson spent working alongside each other. It shows the fruits of a creative relationship that began when Nicholson travelled to Paris to visit Mondrian in 1934, and which would last until the Dutchman's death in 1944.

For Nicholson, his visit to the older artist's studio was something of an epiphany. He compared the experience of entering its monastic, whitewashed interior - punctuated by squares of vivid primary colour - to the "feeling in one of those hermits' caves where lions used to go to have thorns taken out of their paws".

The curators of "In Parallel" have created something similarly shrine-like in two top-floor rooms, the walls of which are hung with around two dozen key paintings and reliefs by Mondrian and Nicholson from the period. Intense, contemplative, ascetic, these are works that are in dialogue with each other yet are not derivative nor obviously the result of a master-disciple dynamic, despite a 20-year age gap.

We see Nicholson, who had already been exploring abstraction, being emboldened to become more angular and geometric. There is a clear progression from 1933 (Six Circles), a loosely carved relief rendered in soft, earthy neutral tones, to the pure and monochrome 1935 (White Relief) or the bold, confident 1937 (Painting), its blocks of muted colour centring inwards around a vivid scarlet square.

For Mondrian, being with Nicholson was an opportunity to take his painting in a subtle new direction, pushing his palette ever further towards white, his blocks of colour receding to the extremities of the canvas, and beginning to use double black lines instead of single. We see the last of Mondrian's "classic" series, Composition with Yellow and Blue, with its spare window-pane bisections of black, white and primary, contrasted with Composition in Red, Blue and White, in which the black lines have thickened and multiplied, almost evicting the colour.

Although Mondrian aimed for absolute abstraction, and flatness of paint, these works are anything but still and lifeless. The paintings pulsate with white dots where the planes meet, while the black lines dance on the canvas. There is simplicity and quiet but also fizzing, kinetic energy. In contrast, Nicholson's meditative reliefs are supposed to be 3D, different levels of painted wood creating subtle plays of light and shade, with gradations in tone where Mondrian uses thick black. They reach their pinnacle in 1936 (White Relief), a column-like oblong of delicately balanced blocks, topped with a perfect circle, crescent moons of shade and reflection outlining it. It looks like the proclamation of an aesthetic alliance and a profound friendship.

The exhibition runs until 20 May