The inquiry — headed by Lord Stevens, the former Metropolitan police commissioner — into the Paris car crash that killed Diana is now trying to obtain the chauffeur’s files from French intelligence but is being delayed by the reluctance of the authorities to hand them over.

Stevens’s team has asked the country’s domestic intelligence service, the DST, to surrender all its “agent handling” files on Henri Paul, the chauffeur, to establish whether he was doing any work for his French intelligence bosses on the night of the crash.

Paul crashed the car, killing himself, Diana and her boyfriend Dodi Fayed in a tunnel in central Paris in 1997. It has previously been claimed — and strenuously denied — that he worked for SIS, the secret intelligence service, also known as MI6.

Well-placed sources say requests by the Stevens team for information about Paul’s activities on the day of the crash, and demands for complete records of tests taken on his blood after he died, have become bogged down by the “incredible bureaucracy” of the French justice system.

The delays mean the £4m inquiry, ordered by the royal coroner in 2004, is certain to stretch into the latter part of this year and may not be completed before 2007.

French police concluded the crash was an accident, caused by Paul driving the Mercedes in which Diana was travelling at high speed away from paparazzi while under the influence of drink and drugs.

The role of Paul, who was deputy head of security at the Paris Ritz hotel, and what he was doing in the hours up to the crash are central to the inquiry. Mohamed al-Fayed, the Harrods tycoon and Dodi’s father who also owns the Paris Ritz, has claimed Diana and his son were murdered by British intelligence.

Scotland Yard sources disclosed last week that the French government had finally confirmed Paul’s employment by the DST during discussions last year.

A Yard source said: “We now know he was working for the French secret service and the French have got to give us access to the records of what he was doing. It’s an issue. We want to know where he was and what he was doing that evening.”

After Paul’s death French police discovered he controlled secret accounts containing more than £100,000 in 14 banks across France.

The Stevens inquiry has been complicated by the apparent refusal of the French authorities to allow Yard detectives to see several key witnesses to the accident.

Stevens has said he is determined to “leave no stone unturned” in his investigation. He needs to establish beyond all doubt whether or not Paul was drunk and under the influence of powerful antidepressant drugs when he crashed the Mercedes.

Concerned that there may have been a forensic mix-up, Stevens is trying to persuade the French public prosecutor’s office to disclose all records of how Paul’s blood was analysed. The Yard team has also had to wait for a new report by Dr Gilbert Pepin, the French toxicologist who analysed Paul’s blood after the crash.

After a wrangle over the size of his fee for acting as an expert witness, Pepin has only recently supplied Stevens with a full account of his analysis of the blood taken from Paul’s body as it lay in the central Paris mortuary.

Stevens is also waiting to interview the female laboratory technician who took the blood from Paul’s body.

Fayed has claimed that MI6 agents visited the morgue on the night of the crash to plant evidence suggesting Paul was drunk, by substituting his blood for the alcohol-contaminated blood of a suicide victim. Sources say there were 25 bodies in the morgue that night.

After two years of investigation, Stevens still takes the view that Diana’s death was an accident. However, he is conscious of the fact that many people still believe she was murdered.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Quitting smoking is contagious, says study
• Cuppa ends round world trip for solo sailor
• British conductor leads Iraqi orchestra