In the novel Timewyrm: Revelation, the Seventh Doctor realizes that, in the alternate universe he visited in "Inferno", the leader of fascist England was that universe's Third Doctor.
There's not much more detail than that. In fact, even that much isn't 100% explicit. If I remember right, he says that it's been bothering him for centuries why the question of why there was an alternate Brig, an alternate Liz, an alternate Yates, etc., but no alternate Doctor, and why the face on all the propaganda posters looked so familiar, and he's finally figured out that it was one of the faces he was offered at his trial in "The War Games". I think this was mentioned again in a later NA novel (I forget which), and very obliquely referred to in the EDA Interference, but no more details were given.
The scene in Revelation was a reference to abortive plans for "Inferno", where Jon Pertwee was to have supplied the voice of a Lord Haw-Haw figure broadcasting to the nature.
Is that what you're thinking of?