Laurence Gardner: Alternative historian whose work helped inspire Dan Brown

Laurence Gardner was a prominent author and speaker in the "alternative history" genre of research and writing, whose eight published works presented often controversial revisionist theories, challenging orthodox views of world history.

He was born Barry Laurence Gardner in Hackney, London, in 1943 and worked at first as a stockbroker in the City before turning towards the arts in general and to writing in particular. His first alternative history work, Bloodline of the Holy Grail (1996), developed ideas that had emerged in Holy Blood and Holy Grail (Baigent/ Leigh/Lincoln, 1982) and in turn provided some of the inspiration for the development of Dan Brown's novel, The Da Vinci Code (2003). Here, Gardner advanced the idea that Jesus had not died on the cross but had instead married Mary Magdalene, fathered children and created a bloodline of descendants which existed through to the present day.

Publishing News spoke of this "...controversial and uniquely comprehensive book of Messianic descent, compiled from the most intriguing histories ever written" and it soon became a top-10 bestseller, as well as being serialised in the Daily Mail.

Around the time this first book was published, Gardner met Michel Lafosse, a modern-day royal pretender, who styled himself "Prince Michael of Albany" and claimed to be a descendant of Bonnie Prince Charlie. Gardner accepted the titles "Chevalier Labhran de St Germain" and a "knighthood" from Lafosse, which he later renounced. Fortunately these false titles – and the various dubious chivalric and royal orders which Gardner and Lafosse created – did not detract from Gardner's subsequent research and writing.

The success of the first book was emulated by Genesis of the Grail Kings (1999), which furnished detailed genealogical research by Gardner to provide a supposed link from Jesus to King Arthur and the Royal House of Stuart. This was followed in 2001 by Realm of The Ring Lords: The Ancient Legacy of the Ring and the Grail, in which Gardner traced the legends of the Ring and Holy Grail through history.

The same year he also worked with the musician Jaz Coleman (best known as the frontman of the post-punk band Killing Joke) on a libretto for The Marriage at Cana, which premiered at The Royal Opera House and related the story of Mary Magdalene and her nuptial relationship with Jesus. Another oratorio, based on the Babylonian creation epic, remained unfinished at the time of Gardner's death.

Perhaps his most controversial work was the 2003 Lost Secrets of the Sacred Ark: Amazing Revelations of the Incredible Power of Gold, which became another bestseller. In this book he expounded his theory of a substance known as monatomic "White Power Gold", which he claimed was used ritually by the ancient Egyptians to provide heightened spiritual awareness. According to the book, The Ark of the Covenant may have been a machine used to manufacture this substance. His most recently published work, The Grail Enigma: The Hidden Heirs of Jesus and Mary Magdalene (2008) continued the "bloodline" theme and explained how the image of Mary Magdalene has been managed and adapted by the Church throughout the centuries.

Aside from his writing, Gardner was an accomplished painter, working on his own and in collaboration with the Canadian artist Peter Robson, who provided the illustration Bloodline of the Holy Grail for Gardner's book of the same name. At the Fine Art Trade Guild he provided his expertise as a Conservation Consultant to define the standards of materials used in printmaking. From 1998 until early this year he was a fellow of the Society of Antiquaries of Scotland, a charitable body which promotes the study of the antiquities and history of Scotland, through archaeological research.

Gardner had worked with the literary agent Andrew Lownie since 2001. Lownie paid tribute to Gardner, saying: "These were ambitious books, based on wide reading and a deep knowledge of a range of subjects, yet he produced a book a year until ill-health forced him to slow down. Laurence became particularly well known in the US, through his popular radio phone-ins. He was a consummate professional – always calm and organised with a gift for imparting complex ideas either through his talks or the written word. A man of nocturnal habits, whose e-mails would generally be sent in the middle of the night, he will be greatly missed."

Marcus Williamson

Barry Laurence Gardner, writer: born Hackney, London 17 May 1943; married Angela (one child, and two children from a previous marriage); died Exeter 12 August 2010.