Transcript for Martin Bashir on Princess Diana's last days

I'm not it's been twenty years since the tragic loss of the people's princess. Who has the words the most popular woman in the world and a new special shows say side of her you haven't really seen before. Here to tell us all about the weeks last hundred days of Diana. Please welcome mark this year. I just want to stop by saying I miss you want innocent they say they say it right. Just to remind this I glossy I don't I don't I don't think this network IM. I NS and I'm gonna get to that but I just want to say that anyway because you think should have notified him that they didn't find me on resigned I was Alabama until all the elements that will set back. Yeah. What are we can't talk about definitely did a quick hits what I think it's time now that's right who are everyone lot Terry you know I can't believe it's twenty years. And you know it was a story that really and the world was captivated by her but. In this piece that you just did your own. Li talking about the last hundred days why did you focus on that well it's interesting because. Her life transformed. In 1996 when she became divorced. So for the first time she was an independent woman. She had a divorce settlement of about seventeen million pounds. And she had decided to remove a lot of the kind of royal protection that went with so she was finding a feat she was becoming more of an independent woman. And she was experimenting in terms of relationships as well and I think for the first time in her life she was to some extent. The woman that she wanted to big someone who was engaged in private she was committed to it so for example she was serving charities involved in the land mines issue. She went to Angola she went. Former Yugoslavia. And she was doing things that gave her a real purpose. And that's what makes the end of the stories and tragic and she had finally found some answers about what god Dodi Pakistan it docked act. Yeah I mean Herman she'd met him two years media and they had a secretive relationship nobody really knew about it. And the problem hobos that. Many people in talking about the relationship. Have said oh well the role family wouldn't be able to tolerate him but actually it was his time. I'm very traditional Pakistani finally which couldn't tolerate the idea. Of being so much in the public high on the tension of that relationship is what spreads through the hundred day. You actually have a lot of where insight into the princess I didn't notice that you have the only extended interview with her back in 1995 cents. What are we going to learn this time around them that we don't know Walt way. The program itself is laid out in two levels there's a kind of for rent music detailed analysis of everything that happened in that last hundred days. Much of wis which we really don't know about. Because she was talking to wish she was going. And it's punctuated in a way that makes all of those facts really needed but at the same time the story you'll says about someone's emotional progression. And how she's torn between this man that she wants to be wind but can't commit to you. And this guy who's chasing had that she's a bit unsure about. And that tension fills the hole of those hundred days so in a way it's not just the facts we as we can identify with some much of that story. I was the amazing thing about the princess she was an inside. But she was an outside. And she gave voice to things that many of us. Have faced like depression planned Weis had post Natal depression severely fined two enough he has. I hadn't heard people talking openly and then suddenly the princess dolls talking about it when she held a baby. Which had inherited HIV. And game it was a step towards. The predicament of ordinary people and it was very moving but all said and powerful because it came from exactly and that and her boys now of course in the last month. Have been doing work for a mental health charity in the UK. Again you know particularly in issues that many of us experienced before and so hard to talk about we have a sneak peek for everyone can you set it up every briefly so that we can. I'm very briefing and at. They say this is a description of the kind of tension that's going on on those last hundred days into Diana's mind about this hot surgeon hasn't com. Yeah he has that was very much knowledge I haven't. Had a really reached in its tether. Because Diana pushed and pushed and pushed him to go public and say we're a couple and he wouldn't he didn't want to. That must've been very painful. Especially for somebody as emotionally. In that you are she'd laws and should it got to the point where it was an ultimatum. I do we go public callable for you know this is not happen is it. I very I had you know I love the first interview did but also I could just not I don't see hypnotized as you should fantastic and. It was a wonderful person in the tragedy of that story is that will never know what might have been because she really had found her feet as a 37 year old woman. And now and in her life was some. Magic like John Kennedy to gender is one of those things that aren't really lead our consciousness. So thanks so much to Martin Bashir the last hundred days of Diana airs Sunday. At 9 PM right here on AV say.

This transcript has been automatically generated and may not be 100% accurate.