Speaking on the BBC Panorama programme she said of Prince Charles's relationship with Camilla Parker-Bowles, she said: "A woman's instinct is a very good one; obviously I had knowledge of it from people who minded and cared about our marriage."
She added: "There were three of us in this marriage so it was a bit crowded. Friends of my husband's were indicating that I was unstable, sick and should be put in a home of some sort to get better so I wouldn't be an embarrassment."
Earlier, she talked of the problems of marrying into the Royal Family. "At the age of 19, you always think you're prepared for everything, and you think you have the knowledge of what's coming ahead. But although I was daunted at the prospect at the time, I felt I had the support of my husband-to-be."
"I think like any marriage, especially when you've had divorced parents like myself, you'd want to try even harder to make it work and you don't want to fall back into a pattern that you've seen happen in your own family.
"I desperately wanted it to work, I desperately loved my husband and I wanted to share everything together, and I thought that we were a very good team. As for becoming Queen it was not at the forefront of my mind. The most daunting aspect was the media attention.''
The Princess revealed that learning her first child was a boy was an "enormous relief". She said: "I felt the whole country was in labour with me. But I had actually known William was going to be a boy, because the scan had shown it, so it caused no surprise."
Describing how she suffered from post-natal depression and did not want to get out of bed in the mornings, she said: "Nobody ever discussed post- natal depression; you have to read about it afterwards."
"It gave everybody a wonderful new label - Diana is mentally unbalanced and that seems to have stuck over the years."
She went on to describe how she harmed herself and became bulimic. "I was ashamed that I couldn't cope and I hurt my arms and my legs. I suffered bulimia for a number of years. That's like a secret disease, you inflict it on yourself because your self-esteeem is at a low ebb.
"People suggested a number of times that I was wasting food. That was pressure in itself."
Discussing her public image she said: "I have always been the 18-year- old girl he was engaged to. I don't think I have been given any credit foir growth."
Because of her comments, pressure grew at Westminster last night for the Prince and Princess of Wales to agree an early divorce to avoid further damage to the monarchy .
Conservative MPs, including ministers, last night said that the Prime Minister's assurance that the Princess of Wales could become Queen was no longer tenable after her acceptance in the interview that the marriage was over.
The controversial interview with Martin Bashir was broadcast following an unprecedented security operation at BBC Television Centre, in west London, with only a handful of senior executives aware of its contents.
Such was the secrecy surrounding the project that three former Royal Marines were detailed to guard the door of the G3 studio in Wood Lane where the programme's titles and credits were being added. At the end of last week the studio, which is normally open to all BBC staff, was swept for bugging equipment in a bid to head off possible leaks.
Prince Charles, who watched the programme at his home, Highgrove, in Gloucestershire, had earlier flown to Kensington Palace, although Buckingham Palace said he had not met his estranged wife. The palace said he had landed at the Princess's home because there was not space for everyone to land on the lawn at Buckingham Palace where the Queen gave a 60th-birthday lunch for King Hussein of Jordan.
As the impact of the Panorama interview began to sink in, senior backbenchers were outspoken in their contempt for the Princess: "Divorce: make her a Duchess and let her go to California. If you take the job you have to take the package," said one source close to the Conservative Party leadership.
The interview with the reporter Martin Bashir, which is thought to have been one of the most-viewed programmes ever shown by the BBC, appears to have hardened views against her at Westminster. There is widespread scepticism over the assurances given by the Prime Minister when he announced to the Commons on 10 December 1992 that Prince Charles and the Princess were separating after 11 years of marriage.
A former Tory whip said: "The idea the Princess of Wales can be Queen is barmy."
The Princess intimated last night that she had no intention of stepping aside quietly.
The broadcast began with her speaking about herself in the third person she said: "She won't go quietly, that's the problem. I'll fight to the end, because I believe that I have a role to fulfil, and I've got two children to bring up."
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