Ever since Russell T. Davies' reintroduced Doctor Who with a modern continuation in 2005, the series has become a worldwide phenomenon. More popular than ever before, "New Who" Doctors David Tennant (the 10th Doctor) and Matt Smith (the Eleventh Doctor), along with current star Peter Capaldi (the Twelfth Doctor), now rank among fan-favorite iterations of the time-traveling alien - shoulder to shoulder with "Classic Who" greats Tom Baker (the Fourth Doctor) and Patrick Troughton (the Second Doctor), among others.

However, in spite of its current success, Davies' first season on Doctor Who was not without criticism, controversy, and scandal - leading to the eventual departure of series star Christopher Eccleston (the Ninth Doctor) after just thirteen episodes. Viewers quickly embraced Eccleston's handsome and whimsical successor, Tennant, but fans have always been curious to know exactly what caused the Ninth Time Lord's brief tenure on the series. For years, Davies and Eccleston have remained mum on the subject; however, in a recent set of interviews, the actor began to paint a slightly clearer picture of why he left the series.

While promoting his new series, ITV's Safe House, Eccleston opened-up about his disagreements with BBC executives as well as his current feelings about the series (and his time as the Doctor).

As mentioned, Eccleston did not address his Doctor Who frustrations in a single interview, so we've listed the relevant quotes (and sources) below - to paint the full picture and put the actor's latest comments into context:

Speaking to the Radio Times, Eccleston discussed film and TV diversity (racial, gender, and cultural inequality) revealing that he had very clear ideas regarding what to do with the Doctor character - specifically addressing his Northern (England) accent:

"I wanted to move him away from the RP (received pronunciation) for the first time because we shouldn't make a correlation between intellect and accent - although that still needs addressing.

I hope I’ll be remembered as one of the Doctors. I have no ill feeling towards the character or the series. I don’t watch it and am not keen to discuss it because I want this to be about Safe House [Eccleston’s new ITV drama]. That’s my mortgage."

However, Eccleston couldn't escape Doctor Who questions - and, in an interview with Daily Record, he elaborated slightly - citing creative differences that lead to his departure:

“I’d had enough. I wanted to do it my way, they wanted something else. We were never going to compromise so it was best to be straight about it and just go [...] It’s very easy to stay in one job and make that your comfort zone, and I want to resist that temptation.”

Eccleston's accent was always a source of discussion (and controversy) - so much that Davies wrote a tongue-in-cheek explanation into the modern series pilot "Rose":

• Rose Tyler (Billie Piper): "If you're an alien how comes you sound like you're from the north?"
• The Doctor (Eccleston): "Lots of planet have a north."

Nevertheless, we can safely assume the Northern accent (and attempt in promoting cultural equality) was only one of the disagreements that Eccleston hints toward. Prior rumors and hearsay have suggested that Eccleston took a stand after certain individuals mistreated the cast and crew - though, at this time, such speculation is little more than gossip. As a result, fans are still left to ponder what else caused a rift between the actor and his BBC bosses - a question that, based on Eccleston's guarded approach to Doctor Who, may never be fully revealed.

Yet, one week prior to this new round of interviews, in a somewhat less defiant moment, Eccleston reflected on his Time Lord: admitting to BBC Radio 4's Loose Ends that if he had it all to do over again, he would have played a few things different - before backing off and restating what he believes to be the most important takeaway from the experience:

“I approached Russell T Davies and said 'I know you are going to do this and I think you should think about me.' I wanted to do something for children, I wanted to learn a lighter way of being.

I think I over pitched the comedy. If I had my time again I would do the comedy very differently. But I think, where I possibly succeeded was in the tortured stuff.

What's interesting in this country is that wherever a story like this emerges they concentrate on the negative. I dont think it's important why I left, I think it's important that I did it in the first place

I'm still there in spirit. Myself and three individuals at the very top of the pyramid clashed, so off I went. But they are are not here to say their side of it, so I'm not going to go into details.

In spite of his brief time in the role, many Doctor Who viewers still hold Eccleston in high regard - even if others claim that, while he succeeded in relaunching the franchise, certain aspects of the Ninth Doctor (and the portrayal) simply didn't land .

As the actor indicates, people tend to focus on the negative - but it's hard to ignore the negative when Eccleston himself remains dismissive in his relationship to the series following his departure. Understandably, he may have held-over frustrations with "three individuals" but were those hurdles so high that the actor couldn't join in the 50th Anniversary festivities (or make a fresh cameo in "The Day of the Doctor" episode)? Eccleston might not want to talk about the reasons he left but it's still hard for many fans to understand why he isn't more interested in participation going forward. Even if Eccleston feels that he was wronged, the most divisive aspect of the Ninth Doctor may be how the actor actually responded in the wake of controversy.

Regardless, change (and regeneration) are all part of the Doctor Who formula - an institution that adjusts for creative differences with fresh blood behind and in front of the camera. Some actors have remained in the role longer than others but, like Eccleston himself states, they're all part of a larger picture: the ongoing adventures of a mad man in a blue box.

NEXT: Doctor Who Viewing Guide: Suggestions & Complete Episode List

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Doctor Who season 9 will air in fall of 2015.

Sources: Loose Ends [via DWN], Daily Record, and Radio Times