One of Britain’s most senior black female officers, who was praised for helping victims of the Grenfell disaster, faces being sacked from the Metropolitan police within days following a criminal conviction.

The force has set a date of 13 March for a fast-track hearing after Supt Robyn Williams was convicted by a jury of possessing an indecent image of a child.

While the Metropolitan Black Police Association has said her targeting was an example of institutional racism, some Met chiefs think the jury verdict means she lied, a claim Williams denies.

Williams was sent an unsolicited video of a child being abused in February 2018 by her sister, who wanted the paedophile behind it hunted down and caught. It was sent via WhatsApp and Williams said she never watched it, which the jury appeared to accept in acquitting her of a charge of covering up knowledge about the video to protect her sister.

Williams is appealing against her conviction by majority verdict in November 2019, and the court of appeal is yet to decide whether it will hear her case.

Williams, 54, is accused of gross misconduct by the Met, with the fact of her conviction being the sole grounds for the discipline charge. If she is found guilty, it is expected her 36-year policing career will end in dismissal.

She is one of the most senior female African-Caribbean officers in Britain and was a founder member of the National Black Police Association and helped to set up a gay police association. She has campaigned for more women in policing and has been awarded the Queen’s police medal.

At the public hearing in west London, Williams will not be allowed to call witnesses but she can be legally represented.

In its notice announcing the one-day hearing, the Met said: “It is alleged that Superintendent Robyn Williams breached the standards of professional behaviour … in respect of discreditable conduct.”

It said the charge amounted to “gross misconduct and is so serious as to justify dismissal”.

Williams is being supported by the Black Police Association and the Police Superintendents Association. Victor Marshall, the latter association’s professional standards coordinator, said: “The Police Superintendents’ Association continues to support Supt Williams throughout this process, and also during her appeal which has been lodged against both her conviction and sentence.”

Explaining the decision to hold a fast-track hearing, the Met said: “A special case hearing carefully considers all the evidence before reaching a decision on whether misconduct is proven and if so what the sanction should be.

“The officer subject to the hearing is entitled to legal representation and the support of the Police Federation or other police representative bodies.”

Williams was sentenced to 200 hours of community service, which she has completed. She remains on the sex offenders register following her conviction, despite the prosecution at her trial accepting she had no sexual interest in children and had never watched the video. She is currently on restricted duties.

Williams told an Old Bailey jury at her trial that she had never seen a video thumbnail image in WhatsApp on her phone that the prosecution said she must have seen and would have alerted her to the child abuse video.

The prosecution told an Old Bailey jury she had lied to protect her sister from potential action for distributing the image and video. Under the law, she had to show she had a lawful reason to have it in her possession.

A jury cleared Williams of corruptly failing to report the video to her superiors but convicted her of possession of it.

Some saw these two verdicts as contradictory and questioned why the Met had pursued her when it had the option not to do so.

It is expected that if the court of appeal decides to hear William’s attempt to overturn her conviction, the Met would consider postponing the hearing at which she faces being sacked.