PRINCESS Diana was killed by an ultra-rare torn vein in one of her lungs, a top pathologist has claimed.

Dr Richard Shepherd claims the injury was so unusual that he had never seen another like it in 23,000 cases.

In his new book Unnatural Causes, he revealed Diana could have escaped the Pont de l'Alma tunnel with a black eye had she been wearing a seat belt.

The book - serialised in the Mail on Sunday - claims her death was a classic "if only case".

He wrote: "If only she had been wearing a seat belt, if only she had hit the seat in front of her at a slightly different angle or slower speed, and if only she had been put in an ambulance immediately after.

"The pathology of her death is, I believe, indisputable. But around that tiny, fatal tear in a pulmonary vein are woven many other facts, some of which are sufficiently opaque to allow a multitude of theories to blossom."

DI COULD HAVE BEEN SAVED
Dr Shepherd, 65, re-examined the princess's body for the official inquiry into her death two decades ago.

Diana, 36, and her lover Dodi Al Fayed, 42, were killed when their Mercedes crashed in an underpass in the French capital in August 31, 1997.

He claimed that Diana could have been saved had paramedics rushed her to hospital instead of assuming she was stable.

He added: "To the ambulance services, she initially seemed injured but stable, particularly as she was able to communicate.