Written before your response...
Seven, What the fuck are you on about? I haven't seen the footage but if someone is restrained and therefore not in the position to cause anymore harm then they shouldn't be kicked in the head no matter how angry someone is. This is a very effective way of killing someone. Brain swelling occurs with head trauma more times than most.
Having worked in the City of Chicago as an EMT/Paramedic, I have seen some malicious and hideous things by the Chicago PD on people who should have known better and not resisted arrest or fought the authorities. The Cops thought it funny to keep taking an injured suspect to the toilet at an emergency room and have him accidentally fall over again and again. I had to patch him up a few times. I was even asked if I wished to assist with his next accident. I politely declined. Over here, there is a fine line that you can either grow up to be a criminal or a Chicago Police officer. Some criminals who shouldn't wear the badge take this path and it's because they like violence. I would assume the British Police would be better trained than that. The Reason I left that job was because I had spent a day restraining 6 to 7 patients (mostly drug addicts who had become violent) and my last call was another one where a psych patient was refusing treatment and had become belligerent. I didn't want to deal with it anymore and called the police for assistance. Turns out it was a scared old man who seemed a little confused and just didn't want to take his meds. The Cops who met me there took great delight in slamming him to the ground and hog tying him and throwing him in our ambulance. Their response was "Thanks Man that was fun, call us anytime". I was appalled and also ashamed that I hadn't assessed the situation beforehand because I was tired and pissed off from an utterly draining day. I quit the next day.
This was about 20 years ago. I still know police officers and some of them are very fine people but the bad apples still exist and are sort of protected over here unless there is body cam footage (there wasn't any back in the day", and there is public uproar.
Anyway, my two pennies worth.
Chicago: Old and Cynical.