His works are characterised by wry humour, the reality of magic and a sustained attempt to reflect on the interaction between religion and politics on a personal and social scale.
A Dangerous Energy was reviewed as "the first Counter-Reformation science fiction novel", and To Build Jerusalem (1995) furthered the story of that particular alternate history.
Whereas A Dangerous Energy focussed on the Church, and To Build Jerusalem on 'high politics', The Two Confessions concerns events in the life of a young would-be industrialist and entrepreneur.
Chafing against the reactionary constraints of his civilisation, he stumbles upon a deep secret from the past and is commissioned (as an expendable person of ill-repute) to solve the associated centuries-old mystery.
The book recounts the Monmouth Rebellion and Battle of Sedgemoor (1685) while adding a layer of fantasy that brings figures from English mythology to life as both combatants and political forces.
Toward the end, as Theophilus engages in pitched battle with Monmouth and his allies, his wife, Eleanor, is simultaneously besieged by supernatural forces in their mansion in Godalming, Surrey.
These depict the adventures of a 17th-century down-at-luck curate who crosses into an alternate Earth where – though all physical features are similar to ours – the hapless local humans are little more than food animals of the monstrous life-form known as Null.
He appoints himself their liberator, goes back for 17th century weapons, and manages to defeat the Null (at least in that world's version of the British Isles) and in the process makes himself a God-Emperor.
But further complications arise from the interference of a power-hungry 19th Century American professor, extraterrestrial creatures known as "Angels" and the exploits of the Emperor's Corps of diplomats.
Whitbourn's Frankenstein’s Legions, a Steampunk and zombie-fiction tinged extrapolation of Mary Shelley's classic gothic tale, was published in both print and eBook form in 2012.
Its title completes that of the first book, citing valedictory words attributed to Hassan i Sabbah, twelfth century founder of the Order of Assassins.
Set a quarter century later, it seeks to provide a 'what happened next?’ to supplement its predecessor's somewhat abrupt ending, whilst paying due homage to Wyndham's masterwork.