William Henry Bragg was a key figure in twentieth century science, serving as President of the Royal Society. With his son Lawrence he won the physics Nobel Prize in 1915 for working out how to determine crystal structures using X-rays. At first they looked at simple crystals but subsequently the method was used for complex organic molecules such as DNA. This portrait was painted while Bragg was Professor at the Royal Institution, living with his family in its second floor flat. It was painted by the window of his study which is above the room where it now hangs. Thirty years later his daughter remembered: 'The artist wore a canary waistcoat, scarlet tie and white socks, and entertained his sitter with a flow of very funny stories not quite to my modest father's taste.