A West Sussex art gallery has won the £100,000 Gulbenkian Prize, beating off three other contenders on the shortlist - including London's Kew Palace.
Pallant House was described as "a jewel of a gallery"
The arts prize - said to be the UK's biggest - went to Pallant House for the flair and sensitivity of its extension.
Professor Sir Colin Wilson, architect of the British Library who died two weeks ago, worked on the design.
The two other contenders were Glasgow's Kelvingrove Art Gallery and Museum and Weston Park Museum in Sheffield.
Judges said they were "won over" by the integration of the modern gallery extension with the original Queen Anne House in Chichester, home to one of the UK's finest collections of 20th Century British art.
They particularly commended the approach of showing a "collection of collections" which reflected the passions of individuals who had made gifts to the gallery.
One collector was Sir Colin, who donated about 400 works worth a total of £5m to the gallery, including a Sir Peter Blake portrait of the Beatles and works by Lucien Freud and Richard Hamilton.
Chairwoman of the judges Francine Stock said the prize, awarded annually, had gone to "a jewel of a gallery".
"The brilliance of Pallant House Gallery lies not only in its thoughtful and intelligent curation, but in the warmth and welcome of the building," the author and broadcaster said.
"There's nothing elitist about the way this fine collection is displayed - intimate yet with space for reflection and tranquillity."
On the shortlist, Kelvingrove, a Victorian gallery and museum that has had a £35m restoration, has what has been called "one of the greatest civic collections in Europe".
Kew Palace, a four-storey red brick house in Kew Gardens in south west London, recently underwent a major restoration - some rooms have been recreated in Georgian splendour, but others have remained untouched for 200 years.
Treasures at Weston Park Museum, which opened in 1875, range from Egyptian mummies to a traditional butcher's shop - it had 55,000 visitors in its first 15 days open after a £19m transformation.
Pallant House trustees have said prize money will go to their endowment fund, which it is hoped will eventually pay for free entry.