The Cabinet of Light introduced the characters of Honoré Lechasseur and Emily Blandish, who were later to star in Telos' Time Hunter range of novellas.
An audiobook of The Cabinet of Light was later released as part of the Time Hunter series and with minor textual changes to distinguish it from Doctor Who.
In 2002, O'Mahony was one of the writers who contributed to Mad Norwegian Press's fictional encyclopaedia The Book of the War, the first in their Faction Paradox series headed by Lawrence Miles.
He has also written the audio dramas Timeless Passages, The Tub Full of Cats and Absence for Big Finish Productions's Bernice Summerfield series.
In 2010 he contributed stories to several of Piper Books' Mature Reading Instruction series of teenage and adult literacy titles.