Meanwhile, Jo continued to believe that the letters to Theo – in which Vincent came through as a romantic figure, a tragic figure – would open his soul to America and beyond. Getting the letters published in English was her ultimate goal.

It was a race against time. Her health was bad – she had Parkinson’s – and the publisher she had signed up with, Alfred Knopf, only wanted to produce an abridged edition, which she would not agree to. She returned to Europe and lived her last years in a spacious apartment in Amsterdam’s stately Koninginneweg and in a country house in Laren. Her son Vincent and his wife Josina approached her, and Jo found happiness in the hour she spent each day with her grandchildren. Otherwise she was remarkably fixated on her life’s work: sending canvases to one exhibition after another, arguing with the publisher, and at the same time dealing with the pain and other symptoms of her illness.

If anything, her obsession seems to have grown as she neared the end of her life. She got into a dispute over modest money with Paul Cassirer, a German trader who had worked closely with her to promote Van Gogh. When a romanticized novel about the van Gogh brothers appeared in German in 1921, she found the factual freedoms it required deeply unsettling. Inquiries for paintings for possible exhibitions came faster and faster – Paris, Frankfurt, London, Cleveland, Detroit – and she stayed closely involved until she could no longer do it. She died in 1925 at the age of 63.

The first English-language edition of the Letters from Constable & Company in London and Houghton Mifflin in the US appeared two years later, in 1927. It contained an introduction by Jo promoting the myth of the suffering artist and emphasizing the role of hers Mannes: “It was always Theo alone who understood and supported him.” Seven years later, Irving Stone published his bestseller “Lust for Life” about the relationship between the van Gogh brothers, which is based heavily on the letters. It again became the source material for the 1956 film starring Kirk Douglas. Until then, the myth was deeply ingrained. No less a figure than Pablo Picasso described van Gogh’s life – “essentially lonely and tragic” – as “the archetype of our time”.

There was one more tribute Jo paid to her brother-in-law and husband, possibly the most notable of them all. Late in her life, when she was translating the letters into English, she had Theo’s remains separated from the Dutch cemetery, where he was buried and reburied next to Vincent in Auvers-sur-Oise. As with the Amsterdam exhibition, she took over the operation like a general, overseeing every detail right through to commissioning suitable tombstones. Hans Luijten told me that he found it an impressive manifestation of her single-minded devotion. “She wanted to have them next to each other forever,” said Luijten.

The excavation of the remains of a man by a woman is such a surprising image that one falls back on the central question of Jo’s life: her motivation. After all, why did she commit to this cause and wear it for the entire length of her life? Certainly her belief in Vincent’s genius and desire to grant Theo’s wishes was strong. And Luijten noticed to me that in promoting van Gogh’s art she believed she was promoting her socialist political beliefs as well.

But people also act for smaller, simpler motivations. Jo’s 21 months with Theo were the most intense of her life. She experienced Paris, joy, a revolution in color and culture. With Theo’s help, she jumped out of her cautious, conventional world and surrendered to passion. As she moved through the museum today, which contains all the paintings that Jo could not part with, another idea emerges: by devoting herself entirely to Vincent van Gogh and selling him to the world, she kept this moment hers Allowing youth to be alive and the rest of us to feel it.