During the liberation of Paris in August 1944, the photographer Lee Miller made her way to Picasso’s studio on rue des Grands-Augustins, where she was greeted with a wide-eyed grin. ‘This is wonderful – the first Allied soldier I’ve seen, and it’s you!’ the artist exclaimed, reaching up to place his hand affectionately around her neck.

Miller had just escaped house arrest for breaching the terms of her press accreditation by entering a combat zone. The PR office of the US Army had dispatched her – one of just four American female photographers they granted an official commission – to Saint-Malo in the mistaken belief that the fighting there was over. As bombs fell, Miller stood by with her camera and, according to her son Antony, caught the use of napalm on film; her negatives were later seized by the censors. She spent her four-day confinement sleeping it off and writing a 10,000-word article on the siege for Vogue.

The choice of publication seems unlikely unless you know that Miller had begun her career as a fashion model. The New Yorker was picked up by Mr Condé Nast himself as she strolled idly into the path of a car but became better known for posing in Hitler’s bathtub as an up-yours to the Nazis following her visit to Dachau. As she made her way surreptitiously through Paris for the liberation, her eye turned only too naturally to the celebratory clothes worn by the other women – the ‘full floating skirts’, the ‘tiny waist lines’. She, for her part, was still dressed in shirt and slacks.

The photograph of her reunion with Picasso is on show at Newlands House Gallery in Petworth as part of an exhibition dedicated to the two artists. It’s hard to imagine two people looking more pleased to see each other than they do.

They first met in the south of France in 1937 where she was holidaying with her future husband Roland Penrose. The exhibition features one of her most atmospheric photographs of their set. Miller’s former lover Man Ray, with whom she trained as a photographer, sits on the grass at a picnic table in Cannes with his newer squeeze, Ady Fidelin, who is topless, poet Paul Éluard and his wife Nusch (also topless), and Roland. They have found a rare clearing; the woods appear to stretch into oblivion behind them.

It’s not clear whether Picasso and Miller were ever lovers, but he certainly fancied her, and, while wary of his charms, she was more than a little taken with him. The number of portraits of Picasso’s long-suffering wife Jacqueline in this exhibition may make you mindful of the raw deal endured by most of the women in this free-loving circle. Miller had certainly tired of Man Ray’s philandering before she married her first husband, the Egyptian businessman Aziz Eloui Bey.

Either way, her relationship with Picasso could be playfully tempestuous. Antony, her son by Penrose, later recalled how, a few days after the liberation, she returned to rue des Grands-Augustins and gobbled up all but one of the tomatoes he had been sketching. When Picasso noticed, he seemed on the verge of giving her a bunch of fives, but paused, turned away, and instead kissed her and pinched her bottom. He had already painted her portrait in peach and yellow with what was, in every sense, a toothsome smile.

Miller’s photographs of Picasso with young Antony are some of the most intimate in the show. In 1950, the Spaniard visited the family at home at Farleys House, not far from the gallery, and made a beeline for the cow pen. Here he found a handsome Ayrshire bull named William. He proceeded to talk to him in French. There’s a lovely photograph by Roland showing his wife, son and Picasso gazing through the railings at the deceptively docile-looking beast.

According to Antony, the colourful drawing Picasso made of three bull-like grasshoppers, displayed in the show, was inspired by William ‘and two of his friends’. Almost two decades had passed since Picasso embarked upon his series of Minotaur prints, but he was still partial to bulls and matadors. Lee Miller recalled how he and her son became so carried away in the rough and tumble one day that they took bites out of one another.

There’s something rather uplifting, not to say sentimental, about looking at the work of two iconic artists through the eyes of the boy they adored. I’d recommend getting your hands on a copy of Penrose’s children’s book, The Boy Who Bit Picasso, as well as his Lives of Lee Miller, to accompany a visit to the exhibition. Do pick up the catalogue, too, in which you’ll find the surprising anecdote that Miller once took first prize in a Norwegian open-sandwich making competition. She was, as Picasso presented her, a woman of many facets.