You don't need any imagination to see the consequences of anything like this happening, if anyone remembers this case...
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That's a 'consequence' not a 'reason'.
The reason it happened is because the towing system failed.
The engineer in me wants to know why the system failed. If indeed it did.
In that photo the trailer stabilisers are deployed.
The jockey wheel is up.
The hitch lock is still attached and empty (so it didn't rip the ball off) and the handbrake is off, so it was possibly being towed (or pulled at least).
The 110 is a late 300tdi or early TD5 (by the snorkle and the style of wing indicator lamps) and is relatively old as that bull bar is ilegal now.
I can't see the safety tie so I assume that is also either stowed or snapped off.
I'd say that was operator error, the hitch wasn't 'snapped' shut on the ball, the driver pulled away and the stabilisers caught on something and flipped the nose up dislocating the trailor from the vehicle.
Either that or some kids took the brake off and pushed it down the hill.
@DCPU what I was looking for was an explanation (from you) of the chain of events that you could imagine that would lead to the PP losing his trailor and Rolls Royce from the back of his Grenny when using an adjustable DB towball.
For example:
Do you think the adjustable plate (which is rated for a 5 tonne pull would rip off ?
Would the Grenny hitch reciever break or pull out of its mounting ?
Would the Avonride hitch fail (it is only held on to the trailers A frame with with 2 x 12mm bolts) ?
Would the 2 pins holding the adjuster plate sympatheicaly snap ?
I asked why do you think the tow system would fail ?
Not, look what happens if and when it does.
How do you go anywhere or do anything ?
Assesment and mitigation of risk with an element of mechanical sympathy sprinkled with common sense.