It would be for the crown prosecution service to decide
Due to all the media would the officer have a right to a fair trial as he is entitled to under the human rights act.
If you look back at the case case re the suspect bomber who was shot it was an officer who was acting in his duty as is the case of the officers during the protest, who can really say what was said or acts displayed by those who attended the protest.
The media love to show footage which they often do edit to make news to put people in a bad light.
The officer would not have done the act to cause any serious injury or death as that is not what they are trained to do and it is very sad that Ian died as a result