Well I'd pretty much be stuck there talking to them until they calmed down enough that I could safely let go and help them up. You tend to have to be a bit creative when you can't use pain compliance or excessive physical force.
Indeed - but no-one is talking about using
excessive force - that would be illegal for the officers just as it would for you.
My point is what would you do if they
don't calm down enough tobe
safely let go in a reasonable time? The answer (which I suspect you know

) is that you would call the police and they would take over and, if justified, arrest (or detain under Mental Health Act or other powers).
Edit: There is an obvious difference in that I'm working in a more contained environment, but the point remains the same, you shouldn't need to punch somebody in order to restrain them.
The difference in environment is a key point. Concerns for the officers would include: does the suspect have a knife or other weapon? does the suspect have friends who will try and attack us / rescue him? are there people around who may take the opportunity of attacking the detainee as we are restraining him (e.g. anyone he has already attacked)? These things all mitigate against any lengthy debate in trying to get compliance with handcuffs. They also need to pick the detainee up (whether or not he is now happy), put him in a van and take him to a police station (all of which means he needs to be handcuffs or he will again become a threat). Some or all of those issues may also apply to you but, as a general rule, you would be usually be able to safely restrain on the ground for longer than they could before having to do something else. You would also usually have a good background knowledge of the person concerned which would advise your risk assessment.
It is the
handcuffing which they are trying to achieve and which is almost impossible without compliance - the punches are a recognised tactic for trying to achieve non-compliant handcuffing (effectively intended to cause a temporary "dead arm"). If you had handcuffs (and lots of non-police people do), and had justifiable grounds for using them, you would be entitled to use that punching tactic to apply them in a non-compliant situation.
Saying that, restraining somebody face down in the first place is probably more dangerous that punching them anyway.
Indeed. Which is another reason why the time available to the police to try and persuade a detainee to comply is restricted - they are only too well aware of the number of deaths which occur due to positional asphyxia during arrest and restraint.
It looked like a punch in the face to me on the video, perhaps I was mistaken.
It's not 100% clear, but there were about three or four punches and certainly most of them hit arm or shoulder and, as I said, that would be a recognised way of trying to overcome resistance to handcuffing. If there were intentional punches to the face, I cannot see that that would be at all justifiable.