Barnes served as the editor of Judge Dredd Megazine from 2001 until December 2005, during which time the title saw a considerable increase in the number of new strip pages. Among other strips, Barnes originally commissioned The Simping Detective. He also wrote a handful of Judge Dredd stories involving alternate universes or featuring a young Dredd.
He worked for five years at Doctor Who Magazine and progressed from writing strips to becoming joint editor in 1998 and sole editor from 2000 until 2002. He subsequently contributed the ongoing Fact of Fiction series of articles to the magazine.
Barnes has written or co-written a number of Doctor Who audio plays for Big Finish Productions.
He has written a number of books on cult films (including James Bond, Quentin Tarantino and Sherlock Holmes) and his book The Hammer Story, co-written with Marcus Hearn, was nominated for the Bram Stoker Award for Best Non-Fiction in 1997