The fourth and finest Doctor, Tom Baker, has reprised the role to finish a Who serial scuppered in 1979 by strike action at the BBC. Shada, penned by Hitchhiker's Guide author Douglas Adams, was supposed to close Doctor Who's 17th season. Location filming in Cambridge and a studio session were completed but the strike nixed further work and the project was later shelved entirely for fear it might affect the Beeb's Christmas-time productions. The remaining parts have been filled in with animation and the voice of 83-year-old Baker, although he also filmed a scene. BBC Worldwide has now relea…