Nearly replied the other day but didn't want be a smart arse but the misinformation is getting too much to ignore.
They're illegal. Not having been pulled is no indication of whether its acceptable. More the case that its a very fringe offence that until there's any major clampdown, most coppers won't know enough about it to know they've got you.
Have a search for Directive 2007/46/EC.
Anything over 750kg needs brakes, which has always been the case. These regulations go further and now prohibit over-run brakes on anything other than centre axle (caravan style) trailers. Which outlaws over-run turntable trailers as are popular on the continent unless they are on air brakes (or other suitable continuous system) and which also catches A-frames as you're still in this case talking about a towed combination which does not have a single set of centre axles, but which is too heavy to fall outside of the scope of the regs.
This came in to force November 2014.
Its never been a grey area, heavy stuff needs brakes and most recovery stuff doesn't have it. But even now A-frame set ups which operate the brakes on the towed vehicle are also no longer legal. Which if you notice has annoyed a lot of motorhome owners as it affects them.
The ONLY dispensation is for recovery to a place of safety. ie. not very far at all. You could possibly use some story to convince someone you've only come from down the road but its a very poor defence and very easy to disprove. Particularly if whatever you're towing has quite clearly not been on the road for some length of time.
One thing I would not rely on is ignorance of the law by those enforcing it. You only need to be out the day the briefing email arrives and you'll be next up.