By Richard Palmer, Royal Correspondent

PRINCESS Diana's death was not an accident and she was right to fear for her safety, a leading barrister claimed yesterday.

Eminent QC Michael Mansfield insisted that Diana's belief that she was under state surveillance was "entirely justified" - and that her fears for a loss of liberty came true as Britain sleepwalked into a "Big Brother" reality.

The barrister said the princess had a "credible and understandable basis" for her worry that she was being spied on because of the threat she posed to the Royal Family and the Establishment, particularly when she campaigned against landmines.

He also claimed there remained many unanswered questions over the events leading to her death.

Mr Mansfield said: "It was utterly reasonable for the Princess to suppose that Big Brother was looking over her shoulder, that her telephone communications were being tapped and her movements were being tracked.

In effect, he argued, we are all living Diana's nightmare.

"Diana's fears for her safety and her preoccupation with surveillance were thoroughly canvassed, and in my view were found to be entirely justified."

Mr Mansfield outlined his concerns about Diana's death and the loss of civil liberties in his autobiography, extracts of which were published yesterday.

The 67-year-old lawyer, who represented Harrods tycoon Mohamed Al Fayed at the inquest into the deaths of his son Dodi and the princess, said there was now CCTV on every corner, cameras tracking cars, satellites tracing mobile phones, credit and debit card records showing people's movements and databases recording medical details and welfare benefits.