3. First Invasion And Use Of London As A Location
Which all brings us to the fact that this was the first ever invasion of Earth in the show's history (and there have been many since) and the fist use of London as a location. In the many years that have followed Earth and more particularly London have featured many times as the targets of alien interest but this was the first. This was the story that truly blended the show mixing up Earth as a location for history stories with outer space as a location for more traditional science fiction stories. Of course London has been done to death as a target location over the years but this was the first time.