MiraiDevant "The problem is that the prevailing attitude is "abuse", "evil" "report" so it is very unlikely that a parent will tell anyone." The point is one asks for help before one starts doing this. Or one does it once or twice, realises that this is a terrible thing to do and looks for alternatives.
"...when the screaming won't stop and you have been trying to deal with a child for hours and hours you can see why parents run out of ideas." If a child is genuinely screaming for hours and hours I would be talking to the health visitor or doctor, as someone else said, and I would be looking to see if the child was in actual discomfort. I'd be thinking about possible autism and some sort of mental or emotional torment or possibly a food allergy causing stomach upsets etc.
Re "You can also see why they smile and hide the difficulties they are facing while they ope the boy will just grow out of it." No, I cannot, I have had lots of issues with my kids, my dd is most likely on the spectrum and is dyslexic, and my son is adopted. I've asked for help from anyone who could give it and I've had help which has made life better.
Re "The "support" isn't really there and now that we have a much more fractured community - it is difficult to find. It is even harder when the children become teenagers." This is only partially true. There is support, we are having help with our dd through CAMHS and we have had a post adoption support for our son. But yes, it is hard to get, you do have to look and ask and be tenacious.
KalaLaka how old is your child. If they are 3 or 4 like the child in the opening post, please think about what you are doing. Please look for help and get it. If your child is a lot older you know your days of being able to force them into the garden are numbered before they stop accepting this unfair treatment.
I am sure the OP could offer to help but I think the first thing the OP needs to do is get this abuse logged with social services or NSPCC.