Wow. Can't believe we took two years to get to it. Just over it, actually. The final piece of the puzzle in answering the question - What if the Doctor had never met Rose Tyler? As we have seen, history has taken a different path through Series 1-4 in this universe, all because the Doctor took a different path instead of the one he did in the basement on Henrik's. From changing the big bad of Series 1 to one that actually made sense to no less than three different versions of Martha running around to the Master being...well, as they would be later in the timeline.
Last time, the Doctor, "Estra", and Donna went off into time and space once more without a Doctor's Daughter to be found. Will Series 4 continue to have a bunch of curveballs thrown at us? Let's take a peek!