Christopher Eccleston's real reason for leaving Doctor Who

In a BBC press release today during promotion for his new project about the life of John Lennon. Christopher Eccelston, gave his real reason for leaving Doctor Who after only one season as "I didn't enjoy the environment and the culture that we, the cast and crew, had to work in" and not as being type-cast as the original BBC press release had said. Or even a ego clash with co-star Billy Piper which had been a rumour under fans of Doctor who. Eccleston went on to say "The fact that he played the Doctor - and not that he had quit - was the most important thing."