On Tuesday, March 12, 2019 at 9:00:06 AM UTC-4, Stephen Struthers wrote:
I have towed large and heavy trailer combinations all over the UK since the

age of 17 (40 years now) and not once have I had a brake issue or for that

matter a tyre issue. We don't use chains and to be honest I not sure I
would want them as the swing of a trailer having "broken away" would
likely cause the towing vehicle to have its own accident. That I would
rather
avoid. Out of interest how many of you have had a trailer break away from
the tow vehicle and what was the cause?

There have been quite a number of tongue failures of Cobra trailers with round tongues, towed almost exclusively by motor homes. Safety chains have kept almost all of them captive to the vehicle which meaningfully reduces the probability of a trailer killing someone else.
One friend noticed his trailer was gone at a fuel stop and drove back 40 miles or so to find it happily stopped in a grass median with no tongue. He was lucky.
The available update to square tongue is a worthwhile improvement if towing with a big vehicle.
UH