Doctor Who has finally revealed the origin of one of the Doctor's most memorable lines. When Russell T. Davies relaunched Doctor Who in 2005, he chose to accelerate the pace, and this was perfectly signified by key lines of dialogue. When Christopher Eccleston's Ninth Doctor first met Rose Tyler, he introduced himself and then told her to "Run for your life!" From that moment on, to become the Doctor's companion was to run.
Nowhere was this better signified than in Matt Smith's debut episode as the Eleventh Doctor, appropriately titled "The Eleventh Hour." Having persuaded the Atraxi not to destroy Earth, the Doctor actually called them back to give them a scolding. He warned the Atraxi they were not the first to test Earth, and encouraged them to figure out why humanity had been able to defeat invaders such as Daleks and Cybermen. They swiftly began bringing up images of different incarnations of the Doctor, prompting the time traveler to delightedly introduce himself. "Hello," he beamed. "I'm the Doctor. Basically, run." It was one of the Doctor's most memorable and iconic lines, signifying just how spectacular a hero, and how fierce a protector, the Doctor had transformed into over the millennia.
Big Finish's latest Doctor Who audiobook, Old Friends, has finally revealed the origin of this line. During an adventure on Earth in the early 21st century, the Ninth Doctor encounters a UNIT operative who recognizes him when he sees the Doctor using the sonic screwdriver. Apparently, the Doctor is discussed in standard UNIT briefing files, and is categorized as a "Level 10." Curious, the Doctor can't help enquiring about what exactly that means and he's told it can be defined as "Basically run."
The Doctor clearly liked this idea and integrated it into his sense of self-identity. The end of Old Friends sets up the Doctor's encounter with Rose Tyler, with his old ally Brigadier Lethbridge-Stewart prompting him that he shouldn't be traveling alone - which means there's a great deal of humor in his constantly talking about running from that point on. Even more amusing, though, is the fact the Eleventh Doctor must have remembered this years later when he faced the Atraxi. The aliens must have accessed the UNIT records to bring up so much footage of the Doctor, meaning the Doctor was summing up what he assumed they'd learned about him from UNIT's files.
Doctor Who is the world's longest-running sci-fi TV series, but in truth, it's long embraced the potential of transmedia, with other mediums taking advantage of the show's potential to tell stories featuring earlier incarnations of the Doctor than the one currently starring in the TV show. In this case, the Christopher Eccleston story essentially serves as something of a prologue to the entire Doctor Who relaunch in 2005. It's the kind of timey-wimey context Doctor Who does best.