Russell T Davies was a master at writing build-ups, even if his climaxes sometimes lacked some of the artfulness of the journey getting there. For this penultimate step in David Tennant's time as the Doctor, Davies introduced a side of the character we'd never seen explored in such depth: the fallible, confused human beneath the alien's surface. Having defied his objectives not to meddle with fixed points in time, the Doctor sees his own importance questioned by the very person he saves, whose sacrifice puts the timeline back on track to the same fate anyway. This Doctor was flawed and at times entirely wrong, and it was the perfect set-up for Tennant's emotionally laden final episodes that followed a week later.
