A trip to London meant a chance to catch up on two exhibitions which began last year and are worth seeing before they end in the next couple of months. Coincidentally the ones that caught my eye are at both the Tates.

At Tate Britain, there’s a large Paul Nash exhibition. Nash, who lived from 1889-1946, was involved in various artistic groupings in the 1930s and a leading figure in British surrealism, though his war paintings were what I knew him for, and after seeing the exhibition still seem to be his most powerful works.

Early works such as The Pyramid in the Sea and Night Landscape saw him influenced by the symbolists and exploring dream-like, often moonlit landscapes.

His First World War paintings and his own experiences made his works bigger, bolder and more dramatically coloured. We Are Making A New World from 1918 has a brave sun peeking over blood-red mountains, a churned up foreground and trees with only the trunks remaining. Ypres Salient at Night is a geometric painting, with light flooding from a sky alight with explosions. The Menin Road has a landscape of destroyed trees, toxic pools of water, a few struggling figures, smoke and light flooding through the devastated sky in straight lines. Spring in the Trenches, Wood Hill 1917 depicts new growth and sun shining over soldiers stuck in a trench. In these paintings dramatic colours not true to life and angular shapes are stunning and spectacular.

After the war, Nash became obsessed with certain places, such as Dymchurch, where he painted The Shore as long straight concrete lines, huge patches of yellow sand and a floaty sky. Other works included still lifes, such as Dead Spring, a plant’s dying greenery soft and twirling against harsh straight lines in the background.

Later works included compositions of objects such as driftwood and stones, and then landscape paintings including objects such as the Avebury stones, or objects representing them.

The Second World War brought along starkness to his work again, including Totes Meer (Dead Sea), inspired by the piles of metal from crashed planes he saw at the Cowley Dump in Oxford, making it into a new shiny sea full of waves.

His final paintings were a return to landscapes involving the moon or sun, and flowers in the sky as precursors of death. It’s a fascinating exhibition and if like me you knew Nash mainly for his war paintings its eye opening.

At Tate Modern, the Robert Rauschenberg exhibition couldn’t be more of a contrast. The artist lived from 1925-2008, and began his career in the 1950s. He came from Texas and only went to an art gallery for the first time after being drafted into the navy.

His first works included a car tyre coated in paint driven over a long strip of paper. Works developed into paintings incorporating found items, and then larger free-standing collages and some works he created live on stage.

There is also the infamous stuffed goad he acquired, and was initially unsure how to evolve it into an art work; eventually it became wrapped in a tyre and stood over a painting. Another work shows a single bed, sheet pulled enticingly back, but the whole coated in paint.

He also worked across art forms, creating sets for more than a decade for the Merce Cunningham dance group, who performed to compositions by John Cage.

Later works included silkscreens consisting of photos enlarged on to canvas, including the recently assassinated President Kennedy, and images from space, science and sport. Another departure was to create Mud Muse, a large tank of clay and water which pops and bubbles as air is released.

Later works took on a political hue, involving influences from countries with repressive governments, and also sculptures made from discarded scarp metal from his home state of Texas, then suffering after an oil crisis.

It’s a hugely varied exhibition and again a learning experience for someone only familiar with a few aspects of his work.

* Nash at Tate Britain continues until March 5, and Rauschenberg at Tate Modern until April 2.