Doctor Who: Why Each Doctor Was Forced To Regenerate
6. The Eighth Doctor (Paul McGann)
Another Doctor who had to wait a good long while to get his regeneration, Paul McGann had to be patient for even longer than Sylvester McCoy did.
At the time, the TV movie was his first and last appearance as the Doctor, and it wasn't until 2013 - 17 years after his debut - that he was given the opportunity to film his regeneration scene, as part of the show's 50th anniversary celebrations.
The Eighth Doctor's end was depicted in the mini-episode The Night Of The Doctor, which shows that he died in a spaceship crash. This lands him on the planet Karn, where he is temporarily "restored" by the Sisterhood Of Karn, who inform him that they can help him choose what his next regeneration should be.
Realising that the destruction of the Time War has to be stopped, Eight decides that there is no need for him to be a healer anymore, and that his next incarnation should be a warrior. Drinking a potion to help him achieve that goal, the Eighth Doctor transforms into the War Doctor, leading directly into The Day Of The Doctor.