Hello Steve,
I am not disregarding or disputing the technical issue here, yes a well-loaded heavy trailer can tow quite happily. But I am amazed that an experienced tow-er would even contemplate yet alone execute such a gross breech of limits.
The dangers of making the trailer heavier than the tow car has often been discussed on this forum. Under normal acceleration and manoeuvres the outfit can be quite manageable, but what happens when you need to make an emergency stop or make some other high speed manoeuvres, the heavier trailer will influence the handling. A significantly heavier trailer will significantly affect the handling and may make a manoeuvre unsafe. I consider that 50mph and loaded as you describe as recklessness.
As I said previously I cannot condone your actions, and whilst I can't claim to be free from transgressions, when it has happened it has never been premeditated or sustained. To my credit I have been points free for 34 years of driving.
I am proud of that, and I would prefer to called goody two shoes than a dangerous driver.
Are you proud of putting your self deliberately on the wrong side of the law, driving without insurance, and endangering yourself and others? I sincerely hope not.