The late Princess of Wales' remark that "there were three of us in this marriage" was watched by 23 million people and inspired the Queen to tell Prince Charles to file for divorce. The Mail's Editor at Large Richard Kay, a royal correspondent at the time, who KNEW Diana, talks us through the build up and the fall out to the interview. Watch analysis from royal editor Rebecca English, Sarah Vine and Richard Eden in a new, must-watch episode of Palace Confidential.

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