FRANCIS BACON’S attempt to paint the perfect portrait is revealed in today’s Times in three previously unseen paintings.

The triptych of self-portraits is considered the closest the artist came to his belief that he was within reach of creating the ultimate likeness. The portraits have come to light only now — 26 years after they were painted and 14 years after Bacon’s death — because he sold them directly to a friend rather than through his gallery.

The buyer, who has never put them on public display or published photographs of them, is selling them at auction for an estimated £5.5 million. The anonymous collector is believed to have paid about £100,000 for the triptych, entitled Three Studies, in 1982.

The triptych is exceptional not least because it survived two years in Bacon’s studio — something of a feat, as he was so destructive that his gallery would take his paintings away as soon as they knew they were finished. Valerie Beston, his personal assistant, regularly came to his studio to remove works while the paint was still drying.

Michael Peppiatt, Bacon’s biographer, believes that the artist held the triptych in the highest regard. “In his later years, Bacon became convinced that he was within reach of the one perfect portrait — the portrait that would sum up and surpass all his other portraits,” he said. “If there had been one ultimate image, it would have to have been heads of himself, such as these Three Studies, which, unusually, he kept and consulted in his studio for a couple of years after painting them.”

Bacon, who was 71 when he created the work, had become preoccupied with his own mortality. He remarked that he was driven to do self-portraits because his friends were “dying like flies”. In particular, George Dyer, his long-term lover, had committed suicide eight years earlier.

Pilar Ordovas, head of evening sales for postwar and contemporary art at Christie’s, said that Bacon almost never sold his work outside his gallery. “There are only two occasions that we know when this happened. The other one he sold to the same person,” she added.

“He must have had some special connection with these paintings — he kept them much longer than usual. Works were usually sold immediately because they were in such high demand. He was the greatest living British artist.”

In his later years Bacon constantly examined himself in the mirror. He also had a collection of photographs of himself, taken by his friend John Deakin, which he kept scattered in his chaotic studio.

His idea of the perfect portrait was not a photorealistic painting, but a picture that captured someone’s personality. “One day people will see how natural my distortions are,” he said. “Very often a person’s appearance belies their qualities, but generally speaking I think that you can, to a great extent, analyse their character from their appearance.”

The triptych also shows his willingness to distort his features. Although Bacon worried about committing an “injury” when he manipulated his friends’ faces, he had no qualms about rearranging his own “old pudding face”.

Three Studies could break the $10 million (£5.8 million) record for a Bacon, set by Study for a Pope (1961) in November. The paintings will go on show at Christie’s in London, on June 16 before the postwar and contemporary art sale on June 22.