Masterpieces by the likes of John Constable, Pierre-Auguste Renoir and Francis Bacon, together valued at more than £200 million, were assembled this week for a free temporary exhibition.
Each of the works is to be sold by auction house Christie's over the coming weeks with many having rarely been seen in public.
Leading the firm's four-week summer season of sales is Constable's The Lock, which is expected to sell for about £25 million.
It is the last of his celebrated series of six works - which includes The Hay Wain - to remain in private hands.
The exhibition, which takes place until Thursday, brings together 50 works estimated to sell for more than £200 million. The 10 leading works are valued at more than £100 million.
Other highlights on display at King Street in London include Francis Bacon's Study for Self-Portrait, from 1964, which experts recently concluded featured the artist's head but the body of his friend Lucian Freud.
Picasso's Femme au chien, from 1962, and Baigneuse by Renoir, painted in 1888, also feature.
There are also works by Basquiat - expected to fetch up to £15 million and set a world record price for the artist - as well as Rembrandt, Freud and Klein.
The coming sales season is said by Christie's to be one of its richest ever with prices likely to total more than £300 million.
Jussi Pylkkanen, chairman of Christie's for Europe, said: "Such an initiative allows us to show the public works of art that have often rarely, if ever, been seen in public."