The parallel lives of the artists is explored in a new exhibit

�After Ben Nicholson first visited Piet Mondrian’s Paris studio in 1934, he recalled that he went to a pavement caf� and sat “for a very long time with an astonishing feeling of quiet and repose”. He compared the atmosphere to “one of those hermits’ caves where lions used to go to have thorns taken out of their paws”. Yet the studio was in a modest apartment above Gare Montparnasse, with shunting trains vying with noise from the dancing school next door.

In the white-painted interior, Mondrian had stuck up different sized squares painted with primary red, blue and yellow. Nicholson was mesmerised by “the feeling of light” and “the pauses & silences during & after he’d been talking”. Four years later, Mondrian was to recreate this studio in a bedsit in 60 Parkhill Road, Belsize Park, after Nicholson had facilitated his coming to London – a wise precaution for an artist who had been labelled “degenerate” by the Nazis.

A new exhibition at the Courtauld Gallery juxtaposes works by the two artists to tell the story of the friendship that began with that first studio visit and lasted a decade until Mondrian’s death.

Mondrian/Nicholson: In Parallel begins with a Nicholson abstract relief from 1933 made a month after his interest in the Dutch artist some 20 years his senior had been sparked. The carving is rough, the painting free – Nicholson described it as “like a section of a primitive game” – and it serves to highlight the changes that took place after he encountered Mondrian’s precision and began making ethereal white reliefs where shadows made lines.

The largest and most celebrated of these, now in the Tate Collection, was carved in 1935 on the leaf of a mahogany table-top which Nicholson bought in Camden Town and carried back to the Mall Studios in Belsize Park – then his home and workplace – on a number 24 bus. He gave a photograph of it to Mondrian who had asked for an example of his work for the wall of his Paris studio.

This exhibition aims to show that the relationship between Mondrian and Nicholson was not that of the established artist influencing the younger man but that they responded to each other’s artistic development. Both were innovators within geometric abstraction who believed art had a spiritual dimension – Mondrian was drawn to Theosophy and Nicholson to Christian Science.

A vital difference was that Mondrian wanted pictures to be “flat” – grids of black lines tied the colour to the surface with movement conveyed through the rhythm of these lines. By contrast, Nicholson’s blocks of colours advance or recede in relation to the others and these and his cut-out forms “fix attention on space as both expanse and depth”, according to co-curator Christopher Green.

The letters and postcards on display – and the catalogue, particularly the essay by Nicholson’s granddaughter Sophie Bowness – are a treasure trove of information about the years when Hampstead was a sanctuary for artists fleeing Continental Europe – including Gabo, Pevsner and Moholy-Nagy.

Mondrian found London conducive to work and a liberating experience. He enjoyed the Evening Standard, dancing at jazz clubs with Peggy Guggenheim and trips to the cinema (he loved Walt Disney) with his “best friends” Nicholson and his future second wife, Barbara Hepworth.

But when war threatened, he declined their invitation to come to St Ives – “nothing there apart from the water” – one from Nicholson’s first wife in Cumbria – “too green” – and instead took a ship to New York. The pair of paintings pictured hangs in the final room – Nicholson’s made in Cornwall, Mondrian’s completed in America. Never again would their work be so close.

n Until May 20 at Somerset House, the Strand. Open daily 10am to 5.30pm. Tickets are �6, �4.50 concessions. Free on Monday 10am to 2pm.