The Macros, originally The Macro Men, was an unproduced story for Doctor Who written by Ingrid Pitt and her husband Tony Rudlin after the former appeared in Warriors of the Deep in 1984.
The couple first got the idea from reading Charles Berlitz' The Philadelphia Experiment, a story about an experiment conducted by the United States during World War II in the attempts to try and make the USS Eldridge invisible to radar. The plot involved the Doctor and Peri arriving onboard the ship in harbour in 1943 where they battled microscopic humanoid life native to Earth but unknown to humans.
After meeting with Eric Saward numerous times, The Macro Men became The Macros and many revisions only resulted in a draft first episode script before all progress was stopped.
Audio adaptation
Big Finish Productions is producing an audio adaptation of The Macros for release as part of its The Lost Stories line. It is scheduled for release in late spring 2010.