Helen Holland suffered serious injuries in the collision in Earl's Court on 10 May. She died in hospital two weeks later.

Now the police watchdog, the Independent Office for Police Conduct (IOPC) has announced it is criminally investigating the actions of the motorcyclist involved in the crash, at the junction of West Cromwell Road and Warwick Road.

The motorcyclist, a police constable, has been told they are under criminal investigation for the offences of causing death by dangerous driving and causing death by careless or inconsiderate driving, the IOPC said.

They are also being investigated for potential gross misconduct - however, that does not mean that charges or disciplinary proceedings will follow.

IOPC director Amanda Rowe said: "Our thoughts remain with Ms Holland's family, friends and everyone affected by her death.

"This is a tragic incident and it is important that we carry out a thorough, independent investigation to establish the full circumstances, which will include the actions and decision-making of the officer under investigation.

"We have been in regular contact with Ms Holland's family and we will keep them updated as our investigation progresses.

"At the end of our investigation, we will decide whether to refer the matter to the Crown Prosecution Service for a charging decision and whether the officer should face disciplinary proceedings."

Investigators attended the scene and police body-worn video footage has been reviewed.

Witness accounts have also been taken after an appeal in the wake of the crash.

In a statement released by Buckingham Palace, Sophie, the Duchess of Edinburgh said her 'heartfelt thoughts and prayers' were with Ms Holland and her family after the incident.

After her death was announced, a Palace spokesperson said: "The Duchess of Edinburgh is deeply saddened to hear that Helen Holland has passed away.

"Her Royal Highness's deepest condolences and sympathies go to all of Ms Holland's family."

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Relatives paid tribute to the great-grandmother as a "beautiful, loving, kind and caring lady who would always put anyone before herself".

In a statement released to Sky News, they described her as "sprightly for her age", adding that "nothing stopped her living life to the full".

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