In season 8,

When Clara jumps into the Doctor's timeline, the Doctor follows her to pull her out. While there, they witness "The Doctor who broke the promise", the promise being the name Doctor.

Who is this Doctor, The Doctor who broke the promise?

Is it one of the actors from the 60's series?
The Doctor who fought in the time war?
Someone else?

At the end of Series 7,

When Clara jumps into the Doctor's timeline, the Doctor follows her to pull her out. While there, they witness "The Doctor who broke the promise", the promise being the name Doctor.

Who is this Doctor, The Doctor who broke the promise?

Is it one of the actors from the 60's series?
The Doctor who fought in the time war?
Someone else?