It has to exist, each story on its own, even without reference to the fourth wall but there are constant, what we used to call in a theatre company I worked with, tagged acts, to bits and pieces of his past, [such as] how the Master arrived on the TARDIS, where has the Doctor been these last few years? Why is he so reluctant to take on his Time Lord duties?

So we get bits and pieces, but it has to exist on its own. Every storyline is going to be, what the writer called ‘Base under siege’ he’s been sent here, there’s a problem, he susses out what the issues are, he brings in the military, he realises their limitations, he goes out to solve it himself.