Family's court battle over 'deluded' Thatcher fan who left all his £8m to the Tory party

Branislav Kostic believed his family were involved in a conspiracy to kill him and only Margaret Thatcher - whom he regarded as the greatest leader of the free world - could come to his rescue.

His will is the subject of an extraordinary High Court battle between the Tories and Mr Kostic's son - who claims his father was not of sound mind when he drew it up.

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In court today, Mr Kostic 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 in the morning."

He said he last saw his father in 1985 and could not contact him because he did not know where he was staying.

"He was living in hotels, living like a nomad."

"Before 1984, my father was a perfectly normal, considerate man."

But he said that he then began to behave erratically, and became abusive towards his mother.

"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 livng in Zurich. My father was paranoid that the female members of my family were trying to poison him."

Belgrade-born Mr Kostic, who built a successful pharmaceutical business in Switzerland and London, died from natural causes in 2005, aged 80. But for more than 20 years he had been suffering from Delusional Disorder, a psychotic illness which made him convinced there was a conspiracy against him involving his family.

In the 1980s he divorced his wife Mirjana and disinherited his son Zoran, while maintaining a

passionate loyalty to the Tory government of the time, the court heard.

Mrs Thatcher, he believed, was 'greatest leader of the free world in history' and would free him of the 'international dark forces' and 'satanic monsters' out to get him.

Having made a will in 1974 which left everything to his family, he changed it in 1988 and again in 1989 to hand all his assets to the Conservatives. That will remained unchanged until his death.

Praising the party for upholding the values of 'freedom and democracy', he called for the money to be used to 'fight the evil and wicked demons'.

At the High Court in London Clare Montgomery, QC, counsel for 50-year-old Zoran Kostic, claimed the will was changed at a time when his father was not of sound mind and was, therefore, not a valid document.

'Rare flashes of insight apart, Branislav had no understanding of his illness, nor of the impact it had on those around him,' said Miss Montgomery. 'Although his disorder was treatable, he did not seek professional psychiatric help.'

Describing Mr Kostic as 'deluded' and 'incoherent', she added that it was 'unthinkable' that, had he been well, he would have left nothing to his son.

Until he fell ill in 1984, Mr Kostic had 'loved and supported' his son who had worked for him part-time after he finished university, she said.

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The Conservative Party Association, however, insists that Mr Kostic was capable of making rational decisions and the will must stand. Mr Kostic, who also admired Winston Churchill and Anthony Eden, was a member of the Conservative Party for more than 20 years and made regular donations at local and national level.

On several occasions he wrote to Tory MP David Mellor asking for help in battling 'dark forces'. One note read: 'These bestial creatures use deceit, dishonesty, misinformation, fear, corruption, thievery, any type of vice and intimidation, blackmail and even assassin to nourish their egotistic, sadistic, satanic and greedy souls.'

Convinced that his enemies were talking to him in codes and signals, he donated £13,000 to the Tories in 1990, believing the sum to be a 'magic number'.

Meanwhile, his family relationships crumbled to such an extent that he refused to visit his mother when she became terminally ill in 1992.

Lawyers for Sir Malcolm Chaplin and Martin Saunders, the chairman and the secretary of the Conservative Party Association, accepted that Mr Kostic was 'eccentric' but said he remained 'skilled and meticulous in matters of business'.

Andrew Simmonds, QC, said: 'His mental illness had no effect on his ability to give rational and clear instructions in relation to his legal affairs, including his divorce.

'Mr Kostic remained capable of managing his property and affairs until his death.'

The case continues.