It is to be displayed for the first time next month as part of an exhibition of rare photographs by the Victorian David Wilkie Wynfield which reveal hitherto unexplored links between British and Impressionist artists.
Wynfield, the great nephew of the distinguished British painter Sir David Wilkie, formed a brotherhood of artists inspired by the Pre-Raphaelites, known as the St John's Wood Clique.
An investigation by the scholar Juliet Hacking has shown that they warmly welcomed Manet on what may have been his only visit to Britain in 1868, when it is thought Wynfield took this striking portrait.
After their encouragement, Manet exhibited in London during the 1870s, including at the Dudley Gallery favoured by the Clique.
Wynfield's portrait of Manet is one of a series of photographs celebrating some of the leading artists of his day, including previously unexhibited portraits of the Pre-Raphaelite painter Edward Burne-Jones and George Du Maurier, the Punch cartoonist.
They are to be included in the exhibition, Princes of Victorian Bohemia: Photographs by David Wilkie Wynfield, at the National Portrait Gallery from 28 January alongside his well-known photographs of the artists John Everett Millais and William Holman Hunt.
Several British galleries have collections of Wynfield photographs, but they duplicate each other. A collection bequeathed to the Royal Academy in London by Wynfield's brother-in-law, William Frederick Yeames, when he retired as the RA's librarian in 1911, has a different selection of works. But the sitters were not identified and the photographs not dated.
When attempts were made to catalogue the works for the Academy, several were wrongly attributed and the collection was eventually consigned to a drawer, known only to scholars. Dr Hacking began to document them when she was working for her Masters degree and eventually realised that the photograph identified as the artist Jules Dalou was, in fact, Manet.
"He has this big bushy beard and it bugged me," Dr Hacking said. "One day, I realised who that face was. Wynfield's pictures are extraordinarily intense. Even people who are quite recognisable in other pictures are quite difficult in his." She has written a book to accompany the exhibition.
Wynfield's virtuosity was acknowledged by the first great woman photographer, Julia Margaret Cameron. She told the art critic William Michael Rossetti that "to my feeling about his beautiful photography I owed all my attempts and, indeed, consequently, all my success".