MI6 men were in Paris when Diana died

MI6 agents were operating in Paris at the time of the car crash that killed Diana, Princess of Wales, and Dodi Fayed, the jury hearing the inquest into their deaths was told yesterday.

The presence of the secret intelligence officers has been used by MohamedAl Fayed to support his allegation that his son and Diana were murdered by MI6 as part of a conspiracy involving the Royal Family. Mr Al Fayed believes MI6 officers used stun guns in the Paris road tunnel on the night of 31 August 1997 to blind the driver of the car carrying Dodi and the princess, causing him to crash into one of the pillars.

Britain's ambassador to Paris in 1997, Sir Michael Jay, is expected to attend the inquest to deny any links between MI6 and a conspiracy to murder the couple.

The coroner, Lord Justice Scott Baker, told the jury: "The UK has maintained from the outset that it was entirely unaware of Diana's presence in Paris."

He also told the jury that Sir Michael had said no officers working for the security or intelligence services were involved in a conspiracy to cause the death of Diana. But the coroner said it was up to the six women and five men jurors to make their own minds up about the reliability of the evidence relating to the alleged involvement of the British secret intelligence services.

Mr Al Fayed also claims the driver of the Mercedes in which the couple were travelling was an agent working for MI6 and evidence was tampered with to portray him as a drunk driver. This, said the coroner, was one of the 10 parts of Mr Al Fayed's conspiracy theory.

Lord Justice Scott Baker said CCTV footage of M. Paul working in the Ritz hotel on the night of the crash showed him to be acting soberly although medical evidence later found him to be twice over the UK legal drink driving limit.

French police twice searched M. Paul's home but found more alcohol on the second visit than they claimed to have found on the first. The coroner said there was "no obvious explanation for this" and told the jury: "You must consider whether there is any sinister implication".

The judge added: "Members of the jury, you will have to decide if indeed samples analysed came from Henri Paul or whether they came from a completely different person." He said the CCTV film showed Mr Paul bending down and tying his shoe laces while working at the Ritz. "There is no indication that his movements were affected by alcohol," he said.

It became clear yesterday that questions of Diana's supposed pregnancy would become a central theme of the inquests.

Mr Al Fayed alleges that the princess was pregnant and this was covered up by the British Government to avoid causing embarrassment to the Royal Family. He claims an unlawful embalming took place in Paris shortly after her death to hide the fact that Diana was expecting a baby.

The coroner said the allegation was important in the context of the Fayed conspiracy theory because it provided a motive for her murder and an explanation for the embalming. But he said there was "no indication given by Diana" either to her close friends and family or her doctor that she was pregnant. In fact, the coroner said the jury would hear evidence later that showed Princess Diana was taking the contraceptive pill. He also reminded the jury that two Home Office pathologists who had examined the body had found no "physical features" supporting that suggestion.

The coroner said that for an embalming to be lawful under French law, authority was required from a French mayor or from French police as well as a member of the deceased's family. But in the case of the princess no family member appeared to have given consent. Instead, it appears that a decision was taken in Paris shortly after her death by her private secretary and Paul Burrell, her butler.

He went on: "It is likely the pregnancy is a matter that cannot be proved one way or the other in scientific terms. 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 said to her friends and intimate details of her personal life."

The coroner said he hoped Mr Burrell would give evidence. He said: "Paul Burrell has made a number of witness statements... I hope that he will come here to give evidence... Paul Burrell, you may think, was in an unrivalled position to know about her and give insight into various aspects of Diana's life. But I am not going to anticipate what his evidence may be."

Another matter for the jury to consider - the whereabouts of private letters sent by the Duke of Edinburgh to Diana – was raised by the coroner, who said that, if indeed they had existed, it seemed they were now "missing". He added that, although Diana's sister, Lady Sarah McCorquodale, was "certain" no such correspondence had existed, Mr Burrell insisted it had. The hearing continues.

How the princess's final evening with Dodi Fayed was caught on camera

5.40pm: Dodi Fayed is pictured leaving the Ritz hotel to go to choose a ring. Mohamed al-Fayed claims this was to be an engagement ring that his son intended to give the princess on 1 September.

5.50pm: The pictures show him returning to the hotel.

4.00pm: CCTV coverage also captured the mid-afternoon scenes outside the Ritz as the paparazzi begin gathering in the square.

6.53pm: The jury is also shown images of the couple's aborted attempt to leave the hotel when they fail to shake off the paparazzi.

9.49pm: A distressed-looking princess is seen being chased into the hotel through the revolving doors by members of the press. The couple have a meal at the Ritz restaurant. Afterwards Diana and Dodi return with their bodyguard, Trevor Rees Jones, to the imperial suite.

Today, the jury will be shown pictures of the couple leaving the hotel for the last time.