A collection of paintings by artists including Picasso, Cezanne and Derain, which lay undiscovered in a vault for 40 years, will be sold in June.
Some 141 paintings belonging to dealer Ambroise Vollard were put in a French bank following his death in 1939 by his assistant who then died.
Although they were discovered in 1979, legal wrangling over ownership mean they are only now coming to auction.
They are expected to fetch up to £16.6m at Sotheby's in London and Paris.
Mr Vollard's assistant, Erich Slomovic, placed the works in the Societe Generale bank before he fled to his native Yugoslavia where he was killed by the Nazis in 1942.
Sotheby's said the "extraordinary works" remained untouched until 1979 when the Paris bank was allowed to open the vault so it could sell the contents to recoup unpaid storage fees.
A planned auction in 1981 was cancelled as the heirs of Mr Vollard and Mr Slomovic began a legal dispute over ownership which was finally resolved in 2006.
Works being auctioned in Paris include Cezanne's Portrait d'Emile Zola
Arbres a Collioure, a 1905 work by Andre Derain - a pioneer of the avant-garde fauve style along with Henri Matisse - will be sold in London on 22 June and has an estimate of £9m to £14m.
When boldly-coloured works completed in the coastal town of Collioure by Derain and Matisse were exhibited at the Salon d'Automne exhibition in Paris in 1905, one critic described the pair as "Les Fauves", which means "the wild beasts".
Helena Newman, vice chairman of Sotheby's impressionist and modern art department, said: "We are very excited to be offering the wonderful landscape by Derain in London in June.
"Its strong, fauve colours and powerful composition, combined with its extraordinary provenance, will be extremely appealing to today's international buyers."
The current record for a Derain is £8.5m, Sotheby's said.
The other 140 works from the collection of Vollard, described by Sotheby's as "the legendary dealer who was at the heart of the exciting developments in the Paris art world in the early 20th century", will be sold in Paris on 29 June.
They include an etching by Picasso as well as Cezanne oil painting Portrait d'Emile Zola and are collectively expected to fetch about £2.6m.