FYI - under the CIL wording a Camper Trailer is deemed to fall under the definition of a Caravan. Any reference to 'trailer' and exclusions etc are relating to a Box Trailer i.e. an open style trailer which can't be sealed. I have this in writing from CIL.
If you have insurance with them, such as I do, on your schedule it reads Caravan - then the description of your camper trailer etc.
I have also been advised sink holes are covered as too river crossings.
However getting bogged below the high tide mark, and subsequently the tide coming in, would not be covered as this would be excluded under 'actions of the sea'.
Hope this helps.
PS I don't work for CIL.
Cheers