Andrew Vicari described Sir Kyffin as an 'extraordinary' gentleman

The artist, who died from cancer last year at the age of 88, left hundreds of works to the National Library of Wales in Aberystwyth.

Experts at the institution said the true significance of the gift would not be fully appreciated for decades.

Heritage minister Rhodri Glyn Thomas said Sir Kyffin's bequest "clearly demonstrates his love of Wales".

And Welsh artist Andrew Vicari told how a piece of work by Sir Kyffin had influenced him throughout his life.

Port Talbot-born Vicari is now one of the world's richest living artists and was once court painter to the Saudi Arabian royal family and government.

To have an artist of this standing giving us these things, really is so important to the nation Paul Joyner, National Library of Wales

He was also the official artist for the first Gulf War and sold his portfolio of paintings from that era for more than �150m.

But it was a tiny painting by Sir Kyffin which he saw in Swansea that had influenced him "more than all the great ones", he said.

Vicari remembered his friend - who he had known since the 1960s - as an "extraordinary man", who had left a "marvellous" legacy.

After Sir Kyffin's death in September 2006, the artist left �500,000 to charities and other bodies in his will, along with hundreds of works to the National Library of Wales.

He also bequeathed the journals he wrote in the last few years of his life to the library, which Vicari said he hoped would be published.

This painting, left to the library, could be worth �1m

"I hope the journals really convey his beautiful personality and his integrity," he said.

"Above all, he was a man of great honour."

Paul Joyner, head of purchasing and donations for the national library, said the journals were significant for a greater understanding of Sir Kyffin the man, as well as his work.

Mr Joyner said they contained writings about Sir Kyffin's paintings, his family, and his social life.

The artist even described how he had seen a ghost on several occasions and found it "quite off-putting".

Mr Joyner said the library's collection would be a "wonderful resource", not only for Sir Kyffin's art, but for people writing books, poetry, or studying aspects of Welsh life.

"He understood the Welsh nature, and a lot of Welsh history and Welsh culture, and that came through in the pictures," he said.

"To have an artist of this standing giving us these things, really is so important to the nation."

'Unique gifts'

Heritage minister Rhodri Glyn Thomas said the national library and the national museum will benefit from his legacy.

"His contribution to the cultural life of Wales cannot be questioned," he added.

During his life, Sir Kyffin also donated a "significant collection" of his works to the Oriel Ynys Mon gallery, and the people of Anglesey.

Described as "unique and valuable gifts" they will form the basis of exhibitions at the �1.5m Oriel Kyffin Williams, which is scheduled to open on St David's Day 2008.

The National Library has said it aims to work closely with the gallery to loan paintings from its own collection.

A spokesperson for Anglesey council said: "We also look forward to working closely with the National Library of Wales in the future, and would, of course, welcome an opportunity to loan and exhibit works bequeathed by Sir Kyffin Williams."