Doctor Who: Why Each Doctor Was Forced To Regenerate

The Eleventh Doctor was one of the brightest and bubbliest Doctors we've ever had, a beacon of light and hope even when things around him were dark and dreary.

And there was no finer display of this than during the final portion of his life, where he spent several hundred years defending the people of Trenzalore from countless alien attacks. The Doctor was their beacon, their saviour, someone they could always count on to have their backs, and whether he was facing Cybermen, Daleks, or Weeping Angels, he was always there to help. He was a Doctor until the very end.

And speaking of that end... it didn't come quickly. The Siege Of Trenzalore stretched on for centuries, and eventually, the Doctor's body just couldn't take it any more, and he started to die of old age. "If you want something done, do it yourself" he quips.

At this point, the Time Lords grant him a fresh cycle of regenerations, but for the Eleventh Doctor, his time is up. With his regeneration energy having restored him to a younger age, he retreats to the TARDIS, bids an emotional farewell to Clara Oswald and an imaginary Amy Pond, and quickly transforms into...