Defining art of the Swinging Sixties is left to the nation

One of the most important private collections of late 20th-century British art has been left to the nation.

Professor Sir Colin St John Wilson, the architect of the British Library, has agreed to make public a collection of 600 pieces that include some of the defining images of the 1960s.

They include Michael Andrew's 1962 study of the Colony Room, which was then the centre of the London art world, and Peter Blake's painting The 1962 Beatles , which he worked on for five years.

Professor Wilson has donated the collection to the Pallant House Gallery in Chichester, West Sussex, where he and his wife, M J Long, have designed a space for the collection.

Another of the art works, Richard Hamilton's Swingeing London has a local connection in that it is an illustration of the arrest of Mick Jagger at a drug bust in nearby West Wittering.

The creation of a new wing at Pallant House will make the gallery one of the most important centres outside London for modern British art.

Professor Wilson's collection is remarkable because of his personal friendships with many of the artists.

One piece, Patrick Caulfield's Portrait of Juan Gris , comes with 30 studies that reveal that the original subject for the work was the French artist Paul Cézanne.

Professor Wilson said it would be "absolutely fascinating" to see all the collection displayed together at the same time.

He said: "It's a very structured collection in the sense that all the artists are personal friends of mine. In many cases I have got not just the final work but the working studies for it because I'm so fascinated by the way that artists work."

He became acquainted with some of the artists when he became a member of the Institute of Contemporary Arts, as well as meeting them at the Colony Room and the nearby "French Pub" in Soho.

The collection also includes Lucian Freud's Self Portrait with Hyacinth in a Pot and works by Frank Auerbach and William Coldstream.

Professor Wilson has made his donation through the National Art Collections Fund.