The poet and author, Mary Russell Mitford (1786 - 1855) is mentioned in a letter from Henneman to Talbot (Reading, 20 April 1847). In the Letter Henneman tells how Miss Mitford sat for her photographic portrait and pleaded that he also take a photograph of her dog. Henneman wasn't convinced the endeavour would be worthwhile as the dog was of a uniform brown colour and was unlikely to remain still during the long exposure. In the end Henneman was proven wrong as the dog did stay still thoughout the 4 minute exposure and the photograph was taken.
