INVESTIGATORS denied millionaire Portland businessman Stephen Curtis was murdered in a horrific helicopter crash.

Police, air accident officers and explosive experts told an inquest there was no evidence the Augusta 109 chopper Mr Curtis was travelling in had been sabotaged.

Earlier, Dennis Radford, father of pilot Max, who also died in the crash near Bournemouth Airport on March 3 last year, claimed the plane had been tampered with by Mr Curtis's enemies.

And Mr Curtis's uncle Eric Jenkins had said his nephew had received threats and predicted be would be murdered just two weeks before the crash.

But yesterday investigators claimed the cause of the accident was likely to have been that Mr Radford, 34, had become 'disorientated'.

Paul Hannant, senior investigator at the Air Accident Investigation Branch, said: "None of the witness statements, the helicopter flight path, or all radio transmissions indicated sabotage.

"All this information showed that sabotage was probably not a factor."

Mr Hannant said that around 7.30pm the helicopter dropped around 600ft before climbing while turning before it crashed into a field at high speed 'nose down'.

He said the pilot's final transmission to the airport control tower included: 'I need to climb,' before the craft plunged into a field and exploded in a fireball.

The jury, sitting at Bournemouth Town Hall, heard visibility was about 2,900 yards, with a few clouds at 1,200ft, around 20 minutes before the crash.

Mr Hannant said it was possible the weather had worsened in those 20 minutes and Mr Radford had been forced to fly using internal instruments. He said there was no record that Mr Radford had flown purely by instruments since May 2000.

Mr Hannant continued: "The most likely cause of the accident was that Captain Radford became disorientated during the final stages of the approach to Bournemouth."

He said it was possible light reflected on a cloud had caused the disorientation.

Mr Hannant added that 18 out of a total of 44 aircraft fatalities between 1997 and 2003 were as a result of pilot disorientation.

John Chappelow, an aviation psychologist, said: "Sudden loss of visual cues can lead to disorientation.

"If you are in an aircraft that is turning, looking down or looking up, you can develop erroneous feelings of climbing or descending."

Mr Chappelow added that without visual cues pilots would transfer to internal instruments to help them land.

He said that instrument flying was a skill that needed to be practised to be maintained.

Bomb expert Sharon Bloom said she found no explosive residue in the chopper wreckage.

Detective Chief Inspector Neil Redstone said there was 'no evidence' to back claims that Mr Curtis, 45, formerly of Pennsylvania Castle, was murdered because he was head of the £16 billion Russian oil business Yukos.

The hearing continues.