Sotheby's has begun the global reveal of one of the most valuable private collections ever offered at auction: twelve paintings assembled in London in the 1970s by Argentine collectors Carlos Pedro Blaquier and Nelly Blaquier de Arrieta, carrying a combined estimate of around $450 million. Five of the works were shown at Sotheby's London on 30 September 2026, with the remainder currently presented digitally before an international tour to Taipei, Hong Kong and Paris ahead of the 18 November evening sale in New York. The centerpiece is Vincent van Gogh's Châtaigniers en fleurs, painted at Auvers-sur-Oise just after the artist left the asylum at Saint-Rémy-de-Provence, roughly three months before his death, and estimated at about $180 million. Helena Newman, chairman of Sotheby's Europe, called it "an incredibly exciting revelation and discovery" and predicted it could set a new auction record for the artist. Paul Cézanne's Arlequin (1888–90), unseen in public since 1975 and the only one of four versions still in private hands, carries a $120 million estimate and is also expected to break the artist's auction record. Claude Monet's Le Jardin des Tuileries was among the works shown in London, alongside four Monets slated for the sale. Newman described the offering as "amongst the most valuable collections ever offered at auction" and "one of really the last moments to buy great museum-quality examples by these key artists of Impressionist and Modern art." Several works have institutional exhibition histories at the Museum of Modern Art, the Tate and the Art Institute of Chicago. The consignment follows the resolution of an Argentine export dispute earlier in 2026, and Sotheby's has guaranteed the full offering, though the guarantee level was not disclosed. The twelve paintings were assembled over decades by a couple who kept the collection largely out of public view; after their deaths in 2020 and 2023, their children are now dispersing it. If the sale meets expectations, it will rank among the landmark single-owner auctions of the decade and could reset price benchmarks for both Van Gogh and Cézanne.