The car crash that killed Princess Diana on on Aug, 31, 1997, was a tragedy that shocked the world. Multiple investigations ultimately attributed her “unlawful death” to the reckless driving of both her chauffeur, Henri Paul, who was ruled to be drunk at the time, and the paparazzi dangerously tailing her limousine.

But two decades later, conspiracy theories endure, with fingers pointing at everyone from the paparazzi and the royal family to the French police and Britain's MI6 foreign intelligence service for their supposed roles in the deaths of Diana and her then-boyfriend Dodi Fayed.

With Aug. 31, 2017, marking the 20-year anniversary of Diana’s death, revisit the unsubstantiated theories surrounding what happened in Paris’ Pont de L’Alma tunnel that night.

Dubbed the "people's princess" by then prime minister Tony Blair, she died after a car crash in Paris on 31 August 1997 aged 36.

On Wednesday, her sons - Prince William and Prince Harry - visited the growing floral tributes being left to her at Kensington Palace.

Harry told members of charities Diana supported, "all of us lost somebody".

The princes are marking the anniversary in private, but other public services are taking place across the UK - including at East London's Mildmay Mission Hospital, which the princess regularly visited when it was a hospice caring for HIV patients.

Former members of staff will share their memories of her, alongside the hospital's patron, actress Linda Robson, and dancer Wayne Sleep, who performed with the princess.

Members of the public have been visiting Kensington Palace, where Diana had lived for more than 15 years during her marriage to Prince Charles and after their divorce.

Mark Lobel spoke to Terry - who had met the princess through his charity work - as he laid roses for her outside the gates.

"It was a privilege [to meet her]," he said. "I was under Waterloo Bridge, giving out blankets and food to the homeless. I don't know what made her come, but she looked down at us all and we were all amazed, just like a little angel came out.

"She spoke to us all. She was very sweet. It was unbelievable. Everybody gave her a smile and she gave them a lovely smile too."