The information is buried somewhere in Gary Russell's book Doctor Who - The Inside Story.

I wonder whether the publication of the extensive 'Fact of Fiction' piece on 'Dalek' is the beginning of a trend. Will we see Matt Jones discuss his abandoned scripts for 'The Impossible Planet'/'The Satan Pit', replaced by Russell's Ood-filled ones, for example? Whose script did 'Tooth and Claw' replace? Etc...