The Conservatives have lost a battle to keep an £8.3m bequest by a man whose son described him as delusional.
Zoran Kostic, pictured, said his father turned to the Tories for help.
Pharmaceuticals mogul Branislav Kostic, who died in 2005, wrote his will in the 1980s after saying Mrs Thatcher would save the world from "satanic monsters".
But his only son Zoran, 50, contested the bequest at the High Court, saying his father was "deluded and insane" and he was entitled to the entire estate.
The Conservatives say they have not touched the money.
Handing down his judgement, Mr Justice Henderson, said Mr Kostic would not have left the money to the Tories if he had been "of sound mind".
He said the decision to leave the whole of the estate to the party was "in part the product of the state of his mind".
Instead he upheld a 1974 will made at a time when nobody disputed Branislav Kostic had full capacity, and under which Zoran was the sole beneficiary.
Following the judgement, Zoran, who lives in Edinburgh, said in a statement that he was "relieved" the case was finally over.
But he said he was "disappointed that the Conservative Party Association made it necessary for my family to come to court and to give evidence on private matters that we found deeply distressing".
He said his father "was a charming, generous and intelligent man who loved his family".
"In 1984 my father became mentally ill. He was diagnosed as suffering from paranoia," he said.
"He was tormented by delusions that I and other members of my family were part of a worldwide conspiracy of terrorists and criminals who were trying to kill him.
"My father refused medical treatment, because he also feared that doctors would harm him. In the grip of his delusions, my father turned to the Conservative Party for help to fight the conspiracy that he imagined.
"He gave them donations and eventually made two wills leaving them everything that he owned."
However, the Tories argued that there were rational reasons why Mr Kostic left his son out of his will when it was rewritten in the late 1980s.
The court heard that Mr Kostic had made the will after saying Margaret Thatcher was "the greatest leader of the free world in history" and that she would save the world from the "satanic monsters and freaks".
Mr Kostic, who was born in Belgrade, died in October 2005 at the age of 80.
His son says his father lacked "testamentary capacity" because of his delusional and paranoid mental illness.
Zoran told the court he grew apart from his father in the mid-1980s.
He said he had worked part-time for his father in 1984 and 1985 at his Transtrade business in London where the two shared a partitioned office.
"During the last months [at his father's office] my father stopped speaking to me completely and would ignore me when he came in the morning," he told the court.
He said he last saw his father in 1985 and could not contact him because he did not know where he was. He said at that time his father was "living like a nomad".
Zoran said that before 1984 his father had been "perfectly normal" but he than began behaving erratically.
He said: "He also began to have paranoid delusions about the female members of his family at this time and slandered my aunt and grandmother, who were both living in Zurich.
"My father was paranoid that the female members of my family were trying to poison him."
Lawyers for the Conservative Party Association earlier told Mr Justice Henderson that Mr Kostic and his son had become estranged and that he was unhappy with his son's career choices.
The party's barrister Andrew Simmonds QC said there was also Mr Kostic's "great and long-standing affection for the Conservative Party and his admiration for Mrs Thatcher".
Mr Kostic set up pharmaceutical and precious metals firm Transtrade UK after being sent to work in London, and became a British national in 1975.
Clare Montgomery QC, representing Mr Kostic's son, said the Conservatives "only benefited because the testator became mentally ill".
Mr Simmonds said that while it was accepted that Mr Kostic had a delusional disorder it was not accepted that this made him incapable of making a proper will.