First (and last) chance to see Sainsbury's bequest

One of the most significant bequests to the nation in a century, including masterpieces by Edgar Degas, Claude Monet, Lucian Freud and Francis Bacon, goes on public display from today.

The exhibition of the 18 masterpieces, at Tate Britain, London, is likely to be the first and last opportunity to view the £100m collection in its entirety before the works are split between the Tate and the National Gallery.

Simon Sainsbury, the British philanthropist and art collector who died in 2006, left the pieces to the two institutions – five to the National, with the rest to be housed by the Tate. Some, such as Freud's Boy Smoking, have not been seen by the public since 1954. Paul Gauguin's Bowl of Fruit and Tankard before a Window has not been exhibited since 1936.

The pieces left to the Tate include three works by Freud, a rare early work by Bacon, Thomas Gainsborough's Mr and Mrs Carter, and three works by the French artist, Balthasar Klossowski de Rola. Two pieces by the French painter, Pierre Bonnard, Nude in the Bath and The Yellow Boat, will make the Tate one of the principal places to see his work outside Paris.

Other works include the gallery's first "conversation piece" by the German painter Johan Zoffany, and an oil painting of a hunt by the English artist John Wootton, who specialised in sporting subjects. The National Gallery will receive impressionist and post-impressionist works, including Monet's Snow Scene at Argenteuil and Water-Lilies, Setting Sun.

Simon Sainsbury had a passionate interest in the arts, particularly 18th and 19th century architecture and art. Sir Nicholas Serota, the director of Tate Galleries, said the gift would "transform" the Tate's ability to show a number of artists in depth. He said it was "one of the most important in the history of Tate" and would greatly enhance its collection.

Nicholas Penny, the National Gallery's director, said the bequest would make a "huge difference to our impressionist and post-impressionist galleries".

The Simon Sainsbury bequest is on display until 5 October