However, what let the episode down for me was Colonel Tia Karim.
For a start, what the hell is she wearing? That’s not a military uniform; she looks like a reject from Topshop! Also, why is her hair down? Military regulations are very strict in that regard and all hair must be worn up when in uniform! And, if she is a colonel, why was she only wearing two rank pips (the insignia for a lieutenant! A colonel has two pips and a crown)? Is she even old enough to be a colonel?
Call me picky but for me such oversights let the episode down. In addition, I would have liked to know exactly why she had nothing left on Earth. What caused her to abandon UNIT in favour of the Shansheeth?