The lead French investigator into Princess Diana‘s death found ‘little clues’ at the scene of the tragic car crash in Paris, including ‘tiny pearls’ belonging to the royal.

Brigade Criminelle chief Martine Monteil, who was first to arrive on the scene, recalled how they found broken car bits, evidence of braking and traces of paint on the vehicle carrying Diana and her lover, Dodi Fayed. Driver Henri Paul also died.

Monteil said she was ‘obsessed’ with finding even the tiniest evidence, like the pearls, because it was all ‘important’ when probing what happened in the Pont de l’Alma tunnel on August 31, 1997.

The officer’s testimony is featured in episode one of Investigating Diana: Death In Paris, a documentary beginning tonight on Channel 4 to mark the 25th anniversary of the tragedy.

The four-part series examines two police investigations into the royal’s death, as well as the conspiracy theories alleging her death was staged by other British monarchs.

The first instalment of the upcoming docuseries follows the immediate aftermath of the crash and investigation led by France’s elite Brigade Criminelle.

‘We started to find these little clues,’ Monteil said of the initial crash scene, in an exclusive clip of the interview provided to Mail Online.

‘We saw signs of braking. Pieces of red light from another car. On the side of the car were traces of paint.

‘I was obsessed with finding things because it’s important.’

Monteil added: ‘I even found some tiny pearls. They belonged to the Princess.’

French detectives reportedly dove straight into the investigation, reconstructing the car’s route and chasing every possible lead. They also were forced to manoeuvre between ‘unreliable witnesses and fallible memories.’

Brigade Criminelle officer Eric Gigou shared how police took the paparazzi into custody and used their photos to piece together the moments before and after the crash.

‘We reconstructed the route they took,’ he explained. ‘Tried to discover all the witnesses, people who might have crossed paths with the car, seen motorcycles, seen something.

‘For us it’s a race against time that started the moment we were given the case because human memory is volatile and over time memories fade.

‘The paparazzi are in custody. From their photos, we could see the last minutes before the accident. We could identify the people around the vehicle in the seconds afterwards.’

Investigators note how they also had to block out ‘countless conspiracy theories’ that sprung up – both in the press and online – almost immediately after the crash.

Monteil and Gigou were among dozens of police officers, medical professionals, firemen and eye witnesses interviewed for the four-part series.

The documentary covers the dual investigation into Diana and Dodi’s deaths, the initial 1997 inquiry by the French Brigade Criminelle and Operation Paget, as well as the inquest into the pair’s deaths. It features interviews with both the French and Metropolitan police forces.

It also probes the Scotland Yard chiefs’ handling of a note detailing Diana’s fears she would be killed in a staged car accident.

Diana voiced her fears to her lawyer, Lord Mishcon, in October 1995. After Diana’s death, he passed his contemporaneous typed account of their meeting to senior Metropolitan Police officers who put it in a safe. But the note was not passed to French authorities investigating her crash for six years.

There have even been suggestions of a mysterious addition to the note, which it has been claimed was designed to give cover to the fact the original note was not released earlier.

The Mishcon Note, as it became known, may well feature in Prince Harry’s upcoming controversial memoir, due later this year ahead of the Thanksgiving and Christmas holidays.

Harry is said to be ‘intensely focused’ on investigating his mother’s final hours. He and his brother, Prince William, had only ‘limited knowledge’ of the 1997 accident and neither were made aware of key details for almost a decade.