Francis Bacon portrait of Lucian Freud expected to sell for over £35m at auction

Francis Bacon’s 1964 portrait of Lucian Freud was based on a photograph, right, taken by their mutual friend John Deakin. Photograph: Sotheby's

A Francis Bacon portrait of Lucian Freud not seen in public since it was first exhibited 57 years ago is to be auctioned with an estimated price of more than £35m.

Sotheby’s on Wednesday announced what is believed to be the most valuable contemporary work to be offered in London in almost a decade.