Show bosses are keeping firm details of Julia's exit under wraps, but her final week on BBC One's daytime soap sees her involved in a terrifying car crash with new love interest Martin Millar (Miles Anderson) - leaving fans to wonder whether the pair will live or die.
Digital Spy recently caught up with Diane to hear about her decision to leave Doctors and her future plans.
How are you feeling now that your time at Doctors has come to an end?
"I'm okay now, but I was very sad to begin with! I filmed my final scenes a while ago, so now I'm excited about the future and playing different parts. That's what actors want - to play lots of different roles - so I'm looking forward to that.
"I'm also having a great time, because I'm catching up with my friends and my family. Being at home is lovely - I think I spent about three weeks catching up on my sleep!"
As it was your choice to leave, how difficult was it to make that decision?
"It was hard, it really was. It took me about two years to make the decision, but eventually I thought that I'd probably taken Julia as far as I could. Lots of different things could happen to her, but I knew her inside out in terms of her character and who she is. So I decided that it was time to move on and do some other projects."
The Doctors cast and crew threw a big leaving party for you, didn't they?
"Yes, it was fantastic. They were so wonderful to me and I was overwhelmed, as there was a lot of love in that room.
"I also loved the fact that I was in one place with them all, perhaps for the first time ever! We don't often get together like that, with all the crew and the office people being there. It was just so wonderful and such a great evening. They were very, very sweet to me."
Looking back over your time at Doctors, do any particular storylines stand out?
"There's lots and lots of storylines which were interesting, but I think one of them was probably the Lyme disease story, where Julia was so ill. That was an amazing storyline, because there was such a wide spectrum of emotions to play.
"I also liked playing the storylines with Julia's family, because it was another side to her that you didn't often see. You'd often see Julia in the office or going out with the girls to the Icon bar, so it was business as usual for Julia - her career seemed to be her life. So when something different came up, it was always great for me to sink my teeth into it."
Will you carry on watching Doctors?
"Oh yes, absolutely. I record it and I never miss an episode. I've always done that - even when I was in the show. It was always interesting to watch because what goes out on screen has usually been filmed two or three months before.
"Also, some of our guest artists are phenomenal - we're so lucky to have had so many good people. And that's not just the well-known people, as some of the young actors who have just come from drama school have been amazing and it's a great honour and privilege to work with them."
Would you appear on another soap?
"Absolutely - why not? They write great parts. Generally speaking, the writing on soaps these days is of such a high quality. You also get great directors and you're working with good people. As I say, I want to play other roles, so if it's a part that I want to play, it doesn't matter what the project is."
As we've seen Julia find love with Martin, do you think they're a good match?
"I think they could be, but she's got to chill out a bit more. She's fighting it all the way, because she's had so many disastrous relationships in her life, so now she tends to take the negative point of view towards how something will turn out.
"Martin's really great because he won't take any nonsense and he's not taking no for an answer. He's forcing Julia to really give it a shot, and she needs that. She's obviously very attracted to him, too, so they could be very good together."
What was Julia's car crash like to film?
"It was phenomenal. We filmed it on a mad, stormy, windy, rainy day. The weather was horrendous, which made things a lot more difficult for everybody when it came to filming. But it was amazing, and in the end the scenes looked incredible because of that. It was very exciting for everybody, as we don't often get to do stunts like that on Doctors."
Do you think The Mill's staff will soldier on without Julia?
"Of course they will soldier on. She runs a very tight ship, so everything's in place and everybody's aware of how things are done. Everybody knows what is needed and required to make it a good practice, so of course they'll manage it."
How would you like Julia to be remembered by Doctors fans in years to come?
"As a great businesswoman with a huge sense of humour, who has an enormous vulnerable streak in her which makes her human. I think she's been a likeable character!"
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Doctors airs weekdays at 1.45pm on BBC One. Julia's exit week begins on Monday, May 14.