The star gave evidence in person on Friday, appearing at the High Court via a video link in a green suit, blue shirt and tie.
He told the court the legal case brought by him and Furnish “contains the most horrendous things in the world that you can ever suffer from a privacy point of view”.
The couple’s legal claim relates to 10 articles published between 2000 and 2015.
In his statement, Sir Elton said he felt “passionately” about “how wrong it is that such gross invasions could have been inflicted upon us and our family and friends without us ever knowing”.
“I have found the Mail’s deliberate invasion into my medical health and medical details surrounding the birth of our son Zachary abhorrent and outside even the most basic standards of human decency,” he wrote in his statement.
Sir Elton said that while he had devoted his life to music, “this does not mean deeply personal things which I have a right to deal with in private are fair game”.
He described what he called the “exploitation of love, connection, trust and bonds to find out information shared in confidence”, and said the “invisibility of such evil acts” meant he and Furnish were unable to detect them.
Addressing the High Court, he said he and Furnish took legal action against ANL because they were “outraged”.
Asked by Catrin Evans KC, representing ANL, if it was true that the couple did not complain at the time the stories were published, Sir Elton said “I can’t remember”.
He added: “We did not know the extent of the seriousness of what had gone on. When we knew the seriousness of what had gone on, we took action, because we were outraged.”
On Thursday, Furnish told the court that one story, published in December 2010, included the publication of their son Zachary’s birth certificate before they had received it.
ANL’s lawyers have argued the story was “entirely legitimately” sourced from previously published reports, the local registrar’s office and a statement from a surrogacy agency.
Evans suggested that information had been put in the public domain before the Mail published its article, but Sir Elton described Zachary’s birth as like an “army manoeuvre”.
“We kept it quiet, which was a miracle considering who we are,” he added.
Evans also told the court that an article with the headline “Sick Elton cancels more tour dates” in November 2009 followed a statement on his website.
In response, Sir Elton said: “That may be the case but we didn’t disclose in the statement on the website my illness or why I was cancelling the tour.”
He added that journalists were “presuming I had something I didn’t have”, but said “I had something far more serious.”
Lawyers for ANL said in written submissions that the social circles of most of the claimants in the overarching case were “leaky”.
They added that Sir Elton’s spokesman at the time of the articles had “regularly provided the media, including Associated journalists, with information about their lives”, including health information.
Sir Elton told the court the spokesman no longer works for him, and that his friends “do not talk to the press and that is why they are still my friends”.
The court case continues.
