Eccleston says his relationship with his three immediate superiors broke down in the first recording block of series 1 and that he will never work with Davies again!
http://www.radiotimes.com/news/tv/2018-03-19/doctor-who-christopher-eccleston-russell-t-davies/
http://www.radiotimes.com/news/tv/2018-03-19/doctor-who-christopher-eccleston-russell-t-davies/