A world famous conspiracy theorist feared murdered by “enemies” vomited two litres of black fluid shortly before he died, an inquest has heard.

Max Spiers, from Canterbury, was found dead by a friend in Poland just days after texting his mother: “Your boy’s in trouble. If anything happens, investigate.”

Vanessa Bates fears her son – who made a name for himself in the shadowy world of conspiracy theorists and sought to expose government cover-ups – may have been murdered because his work “made him enemies”.

Scroll down for video

Now an inquest has heard medical evidence about the moments shortly before his mysterious death, which is being investigated by Polish authorities.

An inquest, opened in Canterbury on Monday, was told the 39-year-old had been visiting Poland to speak at a conference after holidaying with a friend in Cyprus.

In a statement, coroner’s investigations officer Caroline O’Donnell said: “When they returned, Mr Spiers became ill with a high temperature and was weak.

VIDEO: Max's mother speaking in October about why his death should be investigated.

The following day, Mr Spiers vomited two litres of black fluid.

“The friend called a doctor who attempted resuscitation before pronouncing him dead.”

Father-of-two Mr Spiers, who lived in Merchants Way, Canterbury, died in Jozefow, Otwock, on July 16 this year.

His death was initially dismissed as from natural causes by the Polish authorities.

His body was repatriated to the UK but a post mortem examination at Margate’s QEQM Hospital was unable to determine how he had died.

Shortly before his death, Mr Spiers was said to have been probing into the lives of well-known figures in politics, business and entertainment.

Mrs Bates, 63, said: “I think Max had been digging in some dark places and somebody wanted him dead.”

Online, other conspiracy theorists, UFO investigators and bloggers called the circumstances of Mr Spiers’ death suspicious. Coroner Alan Blunsdon told the court he was still awaiting a report from Polish authorities.

He also hopes to secure funding to have Mr Spiers’ laptop and mobile phone forensically analysed.

Mrs Bates is hopeful the investigation will shed more light on her son’s death.

“It’s been a long time coming, but I’m just relieved that at last something is happening and there is a proper investigation and inquest,” she said.

The inquest was adjourned until February 22.