Was Princess Diana's Death A Conspiracy?

10 months before she died, she wrote a letter to Paul Burrel, saying that Prince Charles and/or the British establishment is planning to kill her, in a car accident due to brake failier or serious head injury.And don't you find it interesting how the car they were driving in was stolen two days before the 'accident'?The computer chip was the only thing missing.It was replaced with a different one, and that one could be controlled by a different party.Than in the actual event, Princess Diana's seatbelt was off, actually it wasn't functioning.Was it a comspiracy?