A Renaissance masterpiece by Italian artist Titian has been removed from display at the National Gallery so that its owner can sell the painting.
The painting has been on loan since 1992
The painting, which has hung in the gallery since 1992 was "a significant loss to the public", the gallery said.
Discussions for a joint purchase plan with the National Gallery of Scotland took place when the owner, the Earl of Halifax, decided to put it up for sale.
The gallery said despite "goodwill on all sides" no agreement was reached.
The Portrait of a Young Man has been on loan from the Earl of Halifax to the National Gallery since 1992 and was among many Titian works on display.
Discussions on the painting's future had been ongoing with the Earl of Halifax for the past two years.
"Despite goodwill on all sides, and a shared wish that a purchase for the nation should take place, it has not been possible to reach an agreement that the two galleries could finance," said a statement from the National Gallery.
Portrait of a Young Man will now go on sale from Tuesday, which marks the end of a three-month notice period.
The Earl of Halifax is the deputy chairman of Christie's UK
"As is usual in such circumstances, Portrait of a Young Man has now been taken off display in preparation for packing and return to its owner," the gallery statement said.
A spokesman for Lord Halifax said he would be looking to sell the painting privately, rather than through auction.
"We will be looking at all possible purchasers," said the spokesman.
Earlier this year the earl said he had "very much hoped" the picture would remain on public view, preferably in one of the UK's national galleries.
"But their resources are not unlimited and this kind of commitment is not possible for them at this point," his spokesman said in August.