A painting of the Beatles which the band refused to sign because they felt it was outdated was one of 600 works donated to the nation on Wednesday.
Donator Professor Wilson designed the British Library
Sir Peter Blake, who was behind the band's Sergeant Pepper album, took five years to complete the painting of them.
But when it was finished in 1968, the band's pudding bowl haircuts had been swapped for hippy styles.
The works were given to Chichester's
Pallant House Gallery by private collector Colin St John Wilson.
"By the time he (Blake) did finish it, the Beatles wouldn't sign it, because they said they didn't look like that anymore," said Professor Wilson, who designed the British Library and is also behind an extension at Pallant House due to open next year.
"They were all beads and beards by that time, but I think their decision shows a remarkable lack of a sense of humour," he added.
The collection also includes works by Lucian Freud, Patrick Caulfield, Frank Auerbach, RB Kitaj and David Bomberg.
It is the largest collection given to the National Arts Collections Fund (NACF), through which Professor Wilson donated the gift.
The NACF helps museums up and down the country to acquire works of art.
Professor Wilson began collecting about 50 years ago, after receiving his first pay cheque when he left the navy.
The Beatles painting, titled The Beatles 1962, still features a white space at the top of each figure where the musicians' signatures should have been.
Pallant House Gallery director, Stefan van Raay, said he was delighted at the donation.
"You can imagine how grateful we are to get this enormous collection of more than 600 works of art," he said.
Pallant House is now "one of the most important galleries for modern British art outside London", he added.