Clute and Nicholls, in the Encyclopedia of Science Fiction, identify Hallen as a UK writer. However, a contemporary Australian newspaper notes:
Messrs. Digby, Long and Co., 19 Bornderie-street, Fleet-street, London, E.C., have just published 'Angilin, a Venite King,' by Ambrose L. Hallen, son of Mr. Ambrose Hallen, of Toongabbie. Lance wroto Angilin before he was 21 years of ago.
'Personal', Cumberland Argus and Fruitgrowers Advocate, 4 December 1907, p.2.