Robert Eustace was the pen name of Eustace Robert Barton (1869–1943), an English doctor and author of mystery and crime fiction with a theme of scientific innovation.
Eustace often collaborated with other writers, producing a number of works with the author L. T. Meade and others.
He is credited as co-author with Dorothy L. Sayers of the novel The Documents in the Case, for which he supplied the main plot idea and supporting medical and scientific details.
[1] Barton was born in January 1869, the son of Alfred Bowyer Barton, FRCS, and Editha Helen Howell, of The Green, Hampton Court.
He served in the Royal Army Medical Corps (Temporary Captain) and was awarded the Serbian Order of St. Sava, 5th class.