Britain's greatest art collection on show

They were acquired by the late Paul Mellon, an American Anglophile whose accumulated works rival any of Britain's national collections.

The exhibition, marking the 100th anniversary of his birth, includes more than 150 works from the Yale Center for British Art to which he bequeathed his life's purchases.

Among them are works by Joshua Reynolds, Thomas Gainsborough, George Stubbs, John Constable and JMW Turner, many which of have not been seen in Britain since they were purchased.

John Baskett, Mr Mellon's life-long friend and art adviser, said the collection was so large that only a fraction of it was being hung.

"It's a very limited space in the Royal Academy. It's an exhibition you could easily have done six times over," he said.

He was pleased Mr Mellon was being celebrated. "I'm sure there are people who have hardly heard of him but he gave very substantial sums to British institutions," said Mr Baskett.

" He gave to the Fitzwilliam Museum in Cambridge and to the Royal Academy and he was very generous to the Royal Veterinary College in Camden." Mr Mellon was born in 1907, the son of brilliant banker Andrew Mellon, an American of Scots-Irish descent. The Mellons were among America's great wealthy philanthropists,with the Carnegies and the Fricks.

Thanks to his English mother and holidays as a child, he became an Anglophile, loving foxhunting and racing as well as British art.

For years he was wary of collecting as his father was buying works that eventually became the foundation of the National Gallery in Washington.

The purchase of a Stubbs, entitled Pumpkin With A Stable Lad, in 1936 was a rare early venture into art. His collecting began in earnest in 1960 when he paid £20,000 for another Stubbs, a picture of a zebra. Both are included in the Royal Academy show.

Mr Baskett, who helped with the selection, said: "We did choose pictures that we knew were very close to his heart.

"To buy Pumpkin was brave of him because his father at the time was buying all the great Old Masters from the Hermitage. It was his first striking out on his own." Mr Mellon died in 1999.

An American's Passion For British Art: Paul Mellon's Legacy opens at the Royal Academy on Saturday and runs until 27 January.