By the way, the 85% figure is purely arbitrary and not based on any verifiable data. No-one, and that includes the Caravan Club or other bodies that also support this recommendation, have ever produced any evidence that 85% is substantially safer than, say 90%, or why 80% would not be preferable. I rather doubt whether they would ever be able to substantiate their recommendation.
The fact remains, however, that the higher the weight ratio, the higher the demands made on the driver as to the need for extra due care and attention. For this reason 85% is a good starting point for a novice, but an experienced driver, applying appropriate care under the prevailing conditions, should be able to cope with towing right up to the manufacturer's limit.