Renate Blauel is suing the 73-year-old for allegedly breaching an agreement the pair signed after their divorce in 1988 following a four-year marriage.
In papers filed to the High Court seen by the PA news agency, the pair signed a contract which included a clause preventing either of them from discussing their marriage or the reasons for their separation.
Ms Blauel is now suing Sir Elton over “repeated and flagrant” breaches of the agreement in his 2019 memoir Me and in the biopic Rocketman, also released in 2019.
An Instagram caption posted in September 2017 by the singer which referenced their wedding in Australia is also being referenced in the case.
The fact that the Defendant is gay is now very widely known; it may be one of the most widely-known facts in the world of entertainment
In the documents, Ms Blauel’s legal team said she tried to “shed her identity” by taking steps to conceal her life from the public including changing her name and appearance.
Her claim reads: “As a result of the above breaches, (her) right to privacy and autonomy have been shattered.
“She, and the marriage, have become the subject of widespread press scrutiny and discussion.”
Ms Blauel has asked for an injunction to prevent future public disclosures as well as damages and costs said to be around £3 million.
In papers filed in his defence, the singer’s legal team denied breaching the agreement, arguing the details in the book, film and Instagram post are public knowledge and that the contract “applies only to private and confidential matters”.
Five scenes from Rocketman are referenced in Ms Blauel’s claim including scenes showing their wedding day as well as sleeping in separate bedrooms.
Another scene depicts Sir Elton in a group therapy session discussing the failure of his marriage “on account of his unhappiness and in particular his sexuality,” the claim reads.
Sir Elton’s legal team said that Ms Blauel’s claim does not argue it was a breach of the privacy agreement for Sir Elton to come out as gay.
They add that this reason for the pair’s separation is no longer private and the scenes would be understood by the audience as a portrayal of a gay man in a heterosexual marriage.
The singer’s defence reads: “The fact that the defendant is gay is now very widely known; it may be one of the most widely-known facts in the world of entertainment.”
Ms Blauel also referenced passages of Sir Elton’s memoir Me, which contained details of Sir Elton’s decision to propose, the couple’s wedding, as well as the reception and references to their divorce.
Her claim also said she was particularly upset by Sir Elton writing he did not wish to have children in the marriage, while she said the pair did attempt to conceive.
Her legal team claim the alleged breaches were obvious and that Sir Elton knew they would negatively impact her “jealously guarded” privacy.
In his defence, Sir Elton’s team argued his wedding, which was attended by several celebrities, was subject to widespread coverage and was a matter of public record, as was his divorce.
Ms Blauel claimed the alleged breaches had prompted renewed attention into her life, “destroying her privacy and causing her to suffer severe psychological consequences”.
Sir Elton’s legal team said the singer was unaware of any mental health issues she had.
A source close to Sir Elton told PA: “Elton is shocked and saddened by Renate’s claim after 30 years of a mutually amicable and respectful divorce, especially as he has only ever praised her publicly.”
The source added no mental illness had ever been discussed in the years of friendly correspondence between the pair.
