Diana inquest: Princess was on the contraceptive pill when she died

•Dramatic new CCTV shows Diana's final hours

•Coroner raises doubts that Dodi bought engagement ring

•Prince Philip's letters to Diana 'were stolen'

•Ex-Met boss to be quizzed over 'Diana driver drunk' claim

But the coroner Lord Justice Scott Baker added it may still be impossible to know if the Princess was pregnant when she was killed.

He told the jury that scientific evidence might not be able to demonstrate "one way or the other".

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But he told the panel of 11 people hearing evidence on the deaths of the Princess and her lover Dodi Fayed that they would hear "intimate" details of her personal life.

On the second day of his opening address to jurors at the High Court, he revealed that there was evidence Diana had been on the contraceptive pill and highlighted contradictory evidence over whether she was poised to get engaged to Dodi on the night she died.

He also told the jury that he hoped to call Diana's former butler Paul Burrell to give evidence in person to address many of the areas of dispute.

And he highlighted questions over samples taken from the couple's driver Henri Paul's body which might appear "puzzling".

The couple were killed in a car crash in Paris in the early hours of August 31 1997.

Dodi's father, Harrods owner Mohamed al Fayed, is convinced they were murdered by MI6 under the orders of the Duke of Edinburgh because they believed the Princess was pregnant and might have been about to remarry.

He is also convinced that blood and other samples taken from Mr Paul's body, showing alcohol levels roughly twice the UK drink-drive limit, were switched to give a false reading.

Mr al Fayed insists Diana's calls were being listened to by the secret services, who would have heard her revealing that she was pregnant.

The coroner said the question of whether Diana was pregnant, or even suspected she could be, was relevant in two ways.

"First, her pregnancy or suspected pregnancy is said to have provided the motive or part of the motive for killing Diana," he told the jury.

"Second, her body was embalmed by the French and it is said that the purpose of this was to conceal that she was pregnant."

He said no pregnancy test was carried out on Diana at the hospital where she was taken that night because there appeared to be no reason to do so.

Later, after her death, she was examined both externally and in a formal post mortem examination, where no evidence that she was pregnant was picked up.

But he told the court: "You will hear evidence concerning the extent to which a post mortem examiner can see physical signs of early pregnancy. For obvious reasons, there would not be much to see.

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"You will also hear evidence that Diana was taking a contraceptive pill."

He went on: "It is likely that pregnancy is a matter that cannot be proved one way or the other in scientific terms in this case.

"You will, of course, consider the scientific evidence such as it is but you will also hear evidence from several sources about what Diana had to say to her friends, and intimate details of her personal life."

The jury was also shown today dramatic CCTV images of Diana's final hours. The film, taken by security cameras at the Ritz, showed Diana and Dodi arriving at the hotel, walking through its foyer and then getting into a lift. The images, shown in public for the first time, also showed the paparazzi gathering outside the hotel waiting for the Princess to leave.

In another sensational development, the jury heard today that private letters sent by Prince Philip to Princess Diana may have been stolen.

Coroner Lord Justice Scott Baker told the hearing that it was possible the correspondence could have been taken from Diana's secret chest. He said it was up to the jury to consider the "mystery".