LONDON - Dr Gustav Rau never left anything to chance. When he set his mind to obtaining a painting for his collection, he stopped at nothing to get it. Such was the case with the last self-portrait the aged Edgar Degas painted, shortly before losing his sight, in 1900. On the day it was offered for sale in November 1972, Rau skipped lunch. He knew that British auction houses only rarely adhered to their announced starting times, a practice quite different than today. Quickly eating an apple in his hotel, Rau hurried to the auction, arrived first and successfully bid on Degas’ self-portrait – the other prospects were still at the restaurant.

Dr. Gustav Rau at the opening of his hospital in Ciriri, Democratic Republic of the Congo.

On another occasion nine years later, Rau wanted to bid for a view of Estanque by Cézanne from 1876. He heard on the radio that there would be fog, and determined not to be hindered, Rau decided to travel by ship. On the day of the auction, as airplanes full of collectors were unable to land, Gustav Rau was again able to make the highest bid. Since his day had begun very early, as soon as the hammer dropped, Rau fell asleep in his chair – waking up in time to place the winning bids for a painting of a cypress by André Derain and Raoul Dufy’s Beach at Sainte-Adresse.

The result of this personal endeavour, which spanned more than four decades, is one of the largest private collections of postwar Europe. It is a collection that experts compare to the renowned Thyssen Collection, now in Madrid, or the Bührle Collection in Zurich.

Gustav Rau at the 1983 opening of the children’s medical unit in Ciriri.

Gustav Rau started collecting art in 1958, first acquiring the genre-portrait The Cook (1660/1665) by Gerard Dou, a student of Rembrandt, then subsequently buying hundreds of other artworks. Collecting was possible due to his heritage: his father, a major supplier for Daimler-Benz, was the owner of a manufacturing plant in Stuttgart, which Rau sold for 400 million marks after his father’s death. He himself was a student of medicine, specialising in tropical diseases, pediatrics and gynecology, and in 1977 he established, at his own expense, a hospital and school in Ciriri, in the present Democratic Republic of the Congo (formerly Zaire). Twelve years later, not a single child in the region was dying due to malnutrition. Furthermore, each year Gustav Rau paid the tuition for thirty thousand children in the region.

Several times a year, the collector traveled abroad to purchase art – almost always without an advisor – 
eventually acquiring 743 paintings and sculptures ranging from the late Middle Ages through the early 21st century. His storeroom in Embrach, near Zurich, began to fill up over time, holding such treasures as the Holy Domenikus by El Greco, Holy Jerome by Jusepe de Ribera as well as the diptych Holy Nicholas of Bari/Holy Michael by Fra Angelico. Likewise, Gustav Rau was also the owner of the six-piece cycle of the Porto-Frescoes by Giovanni Domenico Tiepolo, Biblical motifs by Lucas Cranach and Guido Reni, as well as major works by Canaletto and Jean-Baptiste Greuze, Francois Boucher and Jean Honoré Fragonard. Among the Impressionist highlights in Rau’s collection are an exquisite ensemble of Claude Monet's work, including Wooden Bridge at Argentueil (1872), a female portrait by Auguste Renoir as well as an early view by Camille Pissarro, still clearly based on the Barbizon school, together with several paintings by Alfred Sisley.

Rau was collecting more than just paintings: Medieval sculptures and reliefs from the schools of Verrocchio and Riemenschneider, altar crucifixes and Madonnas, candle holders, bowls and faïence, art nouveau vases and china. He was interested in any form of cultural expression.

The Ciriri Hospital, founded by Gustav Rau in the early 1980s, is still in operation today.

However, he deliberately refrained from surrounding himself with these many treasures. Until the mid-1990s, the pediatrician was almost constantly in Africa. Later, Rau lived in Monaco and then near Stuttgart, where his walls were decorated only with portraits of his parents. No one was aware of Rau’s immense collection, although, time and again, he generously – and anonymously – provided loans for museum exhibitions around the world.

It came as quite a surprise when, in 2001, the unmarried and childless collector bequeathed his entire collection to the United Nations Children’s Fund (UNICEF). Suddenly, the incredible scope of Rau’s activity as a collector over almost half a decade was revealed. However, the process was not straightforward, as a protracted dispute about ownership began between precisely those two foundations that Rau had previously established to coordinate his humanitarian activities and his passion for art. It took until 2008 for these issues to be resolved, when a German court ruled that UNICEF was indeed the rightful heir to Rau’s collection.

While still alive, Gustav Rau specified that following his death, a core inventory of the collection was to stay unified and available for public exhibition until at least the year 2026. These 152 paintings, specified by Rau himself, include works by Canaletto and Guido Reni, Monet and Gustave Caillebotte, Édouard Manet and Degas, Renoir and Odilon Redon, Kees van Dongen and André Derain – as well as Pissarro’s Hermitage near Pontoise, one of three paintings he claimed he would never give away as long as he lived.

The Ciriri Hospital, founded by Gustav Rau in the early 1980s, is still in operation today.

Rau determined that the remainder of the collection might be sold at auction by UNICEF, with the proceeds to finance long-term relief programmes for children and, in particular, to support the hospital in Ciriri, which Rau established so many years earlier.

“These sales represent the wish of the German committee for UNICEF to fulfill another part of Gustav Rau’s bequest, who has dedicated his existence to children in need, based on the example of Albert Schweitzer,” says Jürgen Heraeus, Chairman of the German committee for UNICEF. “It was this matter truly dear to his heart, that Gustav Rau ultimately even subordinated his great passion to – the collection of art. UNICEF is now making sure that this exceptional and remarkable legacy may continue, in this way helping thousands of children every single day – just like Gustav Rau had done throughout his entire life. We are grateful and proud to be authorised to fulfill the legacy of this great philanthropist, in the process benefitting all those children of the world – a commitment each collector can rest assured of in full.”

Stefan Koldehoff is arts editor for Deutschlandfunk and has written widely on the Rau collection. He has donated the fee for this article to UNICEF.

[This article originally appeared in Sotheby's at Auction. To subscribe click here.]