Peter Berresford Ellis, born in 1943, is a British historian, literary biographer, and novelist with a substantial bibliography, including over 98 books and 100 short stories published under his own name and pseudonyms like Peter Tremayne and Peter MacAlan. He is particularly recognized for the internationally successful Sister Fidelma historical mystery series. His academic background is deeply rooted in Celtic Studies, holding degrees from the University of London and the University of East London, where he specialized in the field. Ellis has contributed significantly to academic journals and has been acknowledged as a leading authority on Celtic subjects.

Ellis's career began in journalism before transitioning to full-time writing in 1975. His literary output spans historical studies, biographies of notable authors, and popular fiction, including horror and heroic fantasy. He has also been actively involved in various Celtic organizations, holding leadership positions in the Celtic League and Scrif-Celt, and is an honorary life member of the London Association for Celtic Education. His political leanings include support for various independence movements and socialism, which he openly declares as part of his authorial perspective.

Beyond his academic and fictional writing, Ellis has lectured internationally and appeared on television and radio. The popularity of his Sister Fidelma series led to the establishment of an International Sister Fidelma Society. His contributions have been recognized with an Honorary Doctorate of Letters from the University of East London, fellowships from prestigious historical and antiquarian societies, and literary awards from Ireland and France. He is also a Bard of the Cornish Gorsedd for his work on Cornish language and literature.

Peter Berresford Ellis possesses a deep academic foundation in Celtic Studies, holding degrees from the University of London and a master's from the University of East London. This expertise forms the bedrock of many of his published works, where he has explored various facets of Celtic history, culture, and language. He has contributed scholarly articles to prominent journals such as The Linguist and The Irish Sword, earning recognition, including being described by The Times Higher Education Supplement as a leading authority on the Celts. His involvement extends to leadership roles in Celtic organizations, including serving as International Chairman of the Celtic League and chairman of Scrif-Celt, underscoring his commitment to promoting Celtic awareness and scholarship.

Under the pseudonym Peter Tremayne, Ellis achieved significant international success with the Sister Fidelma historical mystery series, which has captivated readers worldwide and led to the formation of an International Sister Fidelma Society. He also wrote adventure thrillers as Peter MacAlan. Beyond these popular genres, Ellis has penned biographies of authors like H. Rider Haggard and W. E. Johns, and explored themes in horror fantasy and heroic fantasy. His prolific output, encompassing both academic and popular fiction, demonstrates a broad literary range and a consistent dedication to storytelling and historical exploration.

Ellis openly articulates his perspective on historical writing, challenging the notion of complete objectivity and advocating for authors to declare their biases. He states, "I write as someone who fully supports Celtic cultural, political and economic independence. Nor do I disguise the fact that I am a socialist." This transparency extends to his support for various independence movements, including those of Chechnya, Tibet, Ireland, and Scotland. His engagement with political and social issues is further evidenced by his involvement with the Labour Party and his honorary life membership in the Connolly Association, dedicated to the study of James Connolly.

“I write as someone who fully supports Celtic cultural, political and economic independence. Nor do I disguise the fact that I am a socialist.”