headline: Microsoft founder's masterpieces on display ahead of blockbuster $1bn auction
text: Masterpieces by some of art's most renowned painters have gone on display before what's expected to be the largest auction in history.
  re collectively expected to fetch a record-breaking $1bn (£900m) at the sale in New York next month.
  works belonged to Paul Allen, co-founder of Microsoft, who died in 2018.
  But while Allen often loaned out his treasures, some art critics fear the auction could lead the works to become hidden from public view for decades.
  Paintings by Lucian Freud, Francis Bacon, Paul Cezanne and David Hockney feature in the collection, which is being auctioned by Christie's.
  150 works will be on public display in the coming weeks at branches of Christie's worldwide, before being auctioned in New York on 9 and 10 November. 
  Fourteen of the paintings will be on display in London this weekend, with other exhibitions set to take place in Paris, Los Angeles and Shanghai.
  While some of the artists come up in auctions relatively often, Allen's collection features pieces that are considered some of the painters' masterpieces.  
  Max Carter, head of impressionist and modern art at Christie's, described it as a "once-in-a-lifetime" auction.
  "I don't think we've had anything like this in terms of masterpiece range across 500 years," he told BBC News. "If you look at the top dozen or so works in the collection, each one of these objects would be a five-year or 10-year defining work if they were to come on the market on their own."
  He added: "The art collecting was very personal [to Allen], in spite of the staggering range - it's 500 years from late 15th Century works by Botticelli through to works executed in the 2010s. 
  "The common thread is this one man's vision. There was no advisor, this was something that he did himself, and buying at the highest levels, decisively and virtually without mistakes, which is something you very seldom see."
  works on display in London include: 
  When he was alive, Allen often loaned his artworks to museums and touring exhibitions. "He was very generous," said Giovanna Bertazzoni, co-chairman of Christie's impressionist and modern art department. "He wasn't private or secluded with the collection. It was always an endeavour that he wanted to share."
  But some arts experts fear that the buyers may hang them on the walls of their homes and restrict them from public view. 
  Melanie Gerlis, Financial Times columnist and editor-at-large of The Art Newspaper, said: "It's always a bit painful to watch works that have been in museum shows - or indeed on long loan to collections - go into the private market, where they may not be seen again by the public.
  "But the truth is that to buy work at these price levels is beyond the reach of museums, so they are always in some way reliant on the generosity of private, wealthy patrons. 
  "I am sure though that many of the next owners the Allen works will be those who are accustomed to lending to museums - and frankly not just for charitable reasons. As most collectors know, a museum showing can greatly add to the value of the work that they own!"
  Asked whether she was concerned that public access to the works could be limited, Ms Bertazzoni said: "I have the same kind of hopes that they will end up in museums. Most of them will be competed for by museums, there are museums that can afford them and they will be in the game. 
  "American collectors are all driven by donating, eventually, to the Met [Metropolitan Museum of Art], to the MoMA [Museum of Modern Art]. It's part of the American tradition. So I really do hope that these works will go back to public fruition."
  money raised by the auction will be distributed between a variety of philanthropic causes Allen supported.
  Allen was a conservationist, and his own foundation aimed to protect oceans and promote biodiversity. During his lifetime, he was also passionate about supporting education, the arts, wildlife, science and technology.