Lord John and the Hellfire Club

Notes

According to the "Foreword" of Lord John and the Hand of Devils, this story first appeared as "Hellfire" in 1998, in the mystery anthology Past Poisons, edited by Maxim Jabukowski. That version was about 12,000 words. The author later expanded the ending, bringing it to 14,000 words. It was then published as an e-book in both English and German (exact date & publisher not stated), but was later dropped from e-publication.
Subsequent publications are included in ISFDB.
Publication date from Amazon.co.uk for ISBN 978-0747275015.
The Wikipedia page for this story says it first appeared as a audio book, but no source is given for this statement and it contradicts what the author herself has written about the story.