At first it seemed like an impossible mystery to solve.

A handsome portrait of a rheumatologist had formed part of the Royal Free Hospital’s collection of 179 oil paintings for many years.

But aside from the man’s profession, nothing about his identity, or that of the artist, was known – another anonymous face from history captured on canvas.

That was until the website Art Detective took up the case, channelling the collective wisdom of the public.

The website was set up by the Public Catalogue Foundation in April in the hope of finding out more about the 17,621 oil paintings by unknown artists in the collections of the National Gallery, the Tate and councils and hospitals nationwide.

The only information the Royal Free had about its painting was that the remover’s label was for Biddick & Co.

But when it appeared on Art Detective it sparked fierce interest.

Public user Alice Gibbs guessed the sitter was First World War doctor Charles Brehmer Heald (1882-1974), after others speculated about the dates of the painting.

The discussion gained pace and another user Paul Kettlewell found a short obituary in The Times.

Curator of 25 years Martin Hopkinson then discovered Dr Heald had been a founder member of the British Red Cross Clinic for Rheumatism and sourced some of his papers and letters, including a manuscript for an unpublished autobiography, from the University of Manchester Library.

While the artist remains unknown, further inspection by the Royal Free showed the painting appears to be an informal one, loosely painted and possibly a family portrait.

Andy Ellis, director of the Public Catalogue Foundation, said: “We are delighted that the unknown rheumatologist has been identified – it shows the power of what can be done when you ask the general public for help.

“In the two years ahead of the launch of Art Detective we used this image in many presentations and always thought someone would know who he was.”

If you fancy yourself as an amateur art historian, get involved by visiting thepcf.org.uk/artdetective/