10 Doctor Who Problems That Time Travel Would Have Solved

10. River Song's Sacrifice

Silence In The Library and Forrest Of The Dead are some of the finest episodes in David Tennant's run as The Doctor, so changing them in any way is heartbreaking. However, once the Vashta Nerada are mollified enough for the survivors to escape, why didn't the Doctor simply nip back in time to warn everyone off? Or explain why the planet was off-limits?

This could have been easily achieved by just dropping some information into the right ears. In fact, over the following years and incarnations, he had plenty of opportunities to warn River herself, as he continued to meet her outside the sequence of time. Why then allow her to die in the manner that he did? And why abandon her, knowing that part of her consciousness lived on in the data core of the planet?

This is never referred to as a fixed point in time and space, so frankly leaving her behind seems to be a cruel move on the part of The Doctor. Perhaps Ten gets the most sympathy here, as he was unaware of the importance of River Song to galaxy. Eleven, Twelve and Thirteen however, that's a different story!