George Dyer Talking, is the most significant large-scale portrait of Dyer to be offered at auction in more than a decade.

A masterpiece by Francis Bacon has become the most valuable piece of artwork ever sold by auction house Christie’s in Europe after going under the hammer for a record £42.2 million.

The 6ft-tall canvas of Bacon’s former lover and muse George Dyer was due to fetch around £28 million but the sale smashed the estimate after being bought by an anonymous buyer over the phone.

Dyer died of an overdose in Paris two days before the painting was displayed at Bacon’s first major retrospective at the Grand Palais in 1971.

The piece, called George Dyer Talking, is the most significant large-scale portrait of Dyer to be offered at auction in more than a decade.

A depiction of Mickey Mouse by acclaimed artist Damien Hirst was also auctioned off for £902,500 with all the proceeds going to children’s charity Kids Company.

Hirst’s work, which represents the figure of the Disney character with a series of large circles, was expected to fetch £300,000, but went for triple that.

Kids Company was founded by Camila Batmanghelidjh in 1996 to provide practical, emotional and educational support to vulnerable inner-city children and currently helps 36,000 children across London and Bristol.

Speaking after last night’s auction Batmanghelidjh said: “Some childlike magic happened tonight.

“£902, 500 was generated through the sale of Damien Hirst’s painting and, in reality, Mickey came to the rescue of some of the most vulnerable children. This money will change lives. From the bottom of my heart thank you, Damien.”

Hirst added: “Brilliant and amazing. Sad to see Mickey go but that is a great result, I’m so pleased to be able to help Kids Company.”

The works were auctioned off as part of Christie’s Post War And Contemporary Art evening auction which takes place in London.

Also included in the sale was a Jeff Koons sculpture depicting a cracked egg.

The most expensive of Bacon’s work was his triptych of Lucian Freud which sold for £85.3 million at Christie’s New York in November 2013.