The court heard that the prosecution was brought after Farrar made a
formal complaint about the policing of the protest. The alleged
assault occurred when police tried to clear protesters away from
flatbed trucks the Met had brought in to help remove parked cars.
Farrar had wanted his members to be able to drive on to the square and
complained to police that they were being treated differently to
black-cab drivers, who were also protesting that day.
He said it was because “the demonstrators came from black and minority
ethnic backgrounds”, Terence Woods, prosecuting, told the jury.
“Black-cab drivers are predominately white British.”
https://www.theguardian.com/uk-news/2020/jan/16/trial-of-union-leader-for-assault-by-megaphone-collapses