Desolation: Part of Zonnebeke, painted in 1918 by William Orpen. Photograph: Imperial War Museum

When Maj William Orpen arrived in Boulogne on April 17th, 1917, his brief, as an official British war artist, was to paint images of the war. Initially, he treated the posting as a bit of a Boy’s Own adventure, travelling in style in a Rolls-Royce with a driver, batman and an aide, as well as a stock of Dewar’s whisky. A sociable Irish man, a mere 5ft 2in tall, he was one of the most successful society painters of the era with a penchant for jokes, painting self-portraits with gnarled features, signing his work with complicated uncials, and frequently referring to himself in the third person as ‘little Orps’.

The majority of artists who came to the front spent a few months or less, but before leaving London Orpen negotiated an unlimited amount of time in France. He was based mostly in Amiens, the centre of Allied headquarters and a key railway hub.

Ready to Start by William Orpen

Nothing in his privileged life had prepared him for what he saw as the barbarism and madness of war. Initially he was unable to capture on canvas the chaos of the battlefields — Tommies dodging bullets as they crawled through rat-infested, water-sodden trenches, or charged across the tortured earth with fixed bayonets. Writing to his wife Grace, he said: ‘It’s like a sudden growing up.’

But after a self-portrait titled Ready to Start, he got into his stride and from then on his output was prodigious. Inspired by the courage of the ordinary soldier, in dozens of paintings and drawings he captured the realism of war in titles such as A Tank in Poziers, Trenches in Thiepval, Studies of Soldiers, and The Thinker on the Butte de Warlencourt, a painting that became a symbol of the war.

Bringing in the Wounded by William Orpen

Maj AN Lee was stationed in northern France and his job was to censor the work of the artists at the front before forwarding their canvasses and drawings to London. Orpen’s relationship with him was spikey. Orpen had a reputation for being sparing of information and explanation about his art; and he was used to working on his own and at his own pace, whereas Lee looked to manage the artists under his control.

Delicate from childhood, Orpen was frequently laid low with colds and fevers but it was a bout of pneumonia coupled with septicaemia that landed him in hospital. There he became smitten with Yvonne Aupicq, a Voluntary Aid Detachment nurse from Lille.

From boyhood, he was a magnet for women, a situation that he reciprocated enthusiastically. In London, he had a wife and three daughters as well as a mistress and a daughter by her. Of necessity, his affair with Yvonne had to be kept secret, but he couldn’t resist painting her. In his next batch of paintings sent to Lee for assessment, he included a scantily-clad portrait of her, titled The Spy. Unsurprisingly, Lee asked for the provenance of the painting, pointing out that the War Office was sensitive about the subject of woman spies since the unfavourable publicity surrounding the deaths by firing squad of Mata Hari and Edith Cavell.

The Spy by William Orpen

Rumour has it that Orpen, pleased at the idea of “getting one over on Lee”, brazened it out, spinning an elaborate tale about while in Paris to do a portrait of a Canadian general, he was offered an opportunity to paint a spy being held in a prison on the outskirts of the city. He explained how he was driven to the un-named prison and brought to the cell of an un-named young girl, who was reciting the rosary.

According to him, she was not afraid of being shot as a spy. Her only wish was to die wearing her own clothes. Her request was granted, her maid obliged and the next morning the girl faced the firing squad wearing her chinchilla and sable coat and a pair of satin slippers. She refused to be blindfolded or to have her wrists tied and as the shots rang out, she dropped the coat and stood naked — her gesture momentarily halting the firing squad. Orpen assured Lee that he knew nothing more.

Wondering had he been too impetuous, he painted another portrait of Yvonne, this time wearing a modest dark blouse and blue jacket. He titled that The Refugee and felt better for having it in reserve.

The Refugee by William Orpen

Reputedly Lee was not satisfied with Orpen’s explanation of how he came to paint The Spy, but he included the canvas in the latest batch of paintings and drawings being sent to London. Some weeks later Orpen was summoned to the War Office to give an account of the painting.

He never revealed what took place behind those closed doors. “Painting any picture outside the terms of his commission from the ministry of information was not permissible to a war artist, but one with such a provocative title particularly so, hence Orpen’s recall to London from France by the censor to explain himself,” says Rupert Maas, the English painting specialist best known for his association with BBC’s Antiques Roadshow. Rumour had it that Orpen was threatened with a court martial as well as being recalled from France. Neither happened. Later Orpen wrote: “I was talked to very severely. In fact, I was in black disgrace. My behaviour could not have been worse, according to Intelligence (F), or whatever they were then called at G.H.Q.” Orpen’s fiction about The Spy was his most elaborate and notorious prank and over time the story has been further embellished in the telling.

In May 1918, an exhibition of Orpen paintings, titled WAR, opened in The Agnew Galleries. It was the talk of London — during the first four weeks more than 9,000 people visited, and takings were in the region of £700. The reviews were mixed, The Times deciding, “Mr Orpen is certainly not a sentimentalist; he seems to paint the corpses with cold, serene skill. His work produced in France adds to our knowledge of himself, but nothing to our knowledge of war.” While the Daily Telegraph wrote about the paintings “vibrating through our hearts”. The poets Wilfred Owen, Siefgried Sassoon and Robert Graves were in unison that the images “were just what was most needed from a war picture”. Orpen, who was still in France, did his best to ignore the subtle and not-so-subtle hints dropped, mainly by officers, about his over-glorification of the fighting men.

The Spy drew a lot of interest, with various versions of the story doing the rounds of dinner parties. Rumours circulated that Lord Beaverbrook, the Canadian-British newspaper publisher and backstage politician, had acquired it. Maj REJ Parsons who had been in hospital at the same time as Orpen, ran into him and Yvonne in Hazebrouck. Orpen led Parsons to believe she was employed by the hotel. When Parsons visited WAR he recognised Yvonne in The Refugee and wrote to Orpen saying how he had enjoyed viewing the paintings, “particularly ‘The Refugee’”. By return, Orpen sent him a postcard, “Hush, hush! Orps”.

Interest in The Refugee and The Spy faded as the war ended and Orpen’s Peace paintings thrust him once more into the public eye, causing either censure or admiration. He died in 1931 and was more or less forgotten until in May 2001 his painting titled Gardenia St George with Riding Crop sold at auction in Sotheby’s London for £1,924.00, the then highest price paid at auction for a painting by an Irish artist.

In 2010 at the BBC’s Antiques Roadshow in Greenwich, The Refugee was presented for assessment to Rupert Maas. Around the same time, the late Chris Pearson, an Orpen expert, found a letter in the Beaverbrook archives from Orpen thanking Lord Beaverbrook for getting him off the hook over the picture.

“The version of ‘The Refugee’ brought to us was inscribed Mailliw Nepro, as I recall, not exactly a uncial, but of course Orpen backwards,” says Maas. “Painting any picture outside the terms of his commission from the ministry of information was not permissible to a war artist, but one with such a provocative title particularly so. The assumption was that this was done as a gift for Lord Beaverbrook. In short, Orpen painted two of ‘The Refugee’. The Imperial War Museum deemed the Roadshow version fake but they were wrong.”

Orpen at War by Patricia O’Reilly is published by Liffey Press on September 24th