Fathoms of Doom (unproduced novel)
From Tardis Wiki, the free Doctor Who reference
Fathoms of Doom was one of three novels which Mark Gatiss initially pitched to the BBC Past Doctor Adventures, alongside The Roundheads and Cromwell's Dust. Roundheads would be the only novel commissioned, but Gatiss still hoped to write the other two stories. When Bill Baggs later asked Gatiss for scripts for Audio Adventures in Time & Space, Gatiss repurposed Fathoms of Doom into the audio story Island of Lost Souls, renaming it to avoid the BBC's attention. (REF: Downtime – The Lost Years of Doctor Who)