The legal position is 'if the trailer has brakes they have to work'. 'If the trailer is under 750 kg it does not need brakes'.
So what if you have a trailer with the brakes removed that is under 750kg. Just because a thing looks like it might have brakes does mean it has. See many small home made trailers based on car axles running with the drum in place as a spacer. So when is a decommissioned brake system not a brake system? I have used this loophole with the dolly often. After all if the car is a trailer it is not a car. Take out the brake shoes, no brakes fitted.
It is on this argument that we defeat the other fav 'A car with its wheels on the road has to be MOTed and Taxed'. A dolly with a car on is clearly not a car nor is the car behaving as a car. It is behaving as a trailer. Dead cars can be moved by dolly. A car on an A frame is behaving as a towed car would. It is a rigid tow, if you like. That is the difference between the two methods and why emergency vehicles favour spectacle lifts over rigid towing. The dead and unroadworthy, often brake-less, cars can be removed and transported round the country to garages, scrapyards etc. Even new cars can be seen to be moved in this way. So we are back to trade using the things OK.
I stopped using either frames or dollys in Europe sometime ago. I think Germany is on emergency vehicles only. France the same? Not sure about the low countries. Spain, apparently on no account. So the law is confused but clearly the drift is towards banning them save for emergency vehicles who need to be able to clear a mess efficiently. I expect this gets rolled up in operators licences and trade insurance cover not available to anyone else. INdeed we are fortunate to still be allowed to make home made trailers!
Being a microcar owner of the old school therefore we are going to do it, aren't we? Microcars, falling through the loopholes of the law. It is one reason to have them surely. Two fingers to the establishment and nanny state.