In 20+ years of trailer tent and caravan insurance no incidents. But is it worth the risk of deleting the add on. It is the one time when the van is most subject to the close proximity of slow moving vehicles reversing blind, tired drivers after a 300 mile trip at there least alert.
I'm only paying £200 for £31.5K of total insurance with a £100 excess. I don't think you would save yourself much.
Colin