Bailey Olympus 504 - wheel came off whilst driving

Our Bailey Olympus 504 is 2 years old and serviced each September annually. Upon 15 miles into our journey home towing on Friday, our wheel came off the caravan, luckily only going at 25 mph through a village.

It has caused extensive damage to the wheel hub, side panel, chasis and internal damage and has to get a repair quote directly from Bailey manufacturers in Bristol.

My question is, if anyone knows under insurance policies whether this scenario is classed as "mechanical failure", whereby that is an exclusion to the caravan insurance policy?

Looking up a general definition of this term, it means:

"Definition:  Mechanical Failure - Loss of the load-carrying capacity of a component or member within a structure or of the structure itself initiated when the material is stressed to its strength limit, thus causing fracture or excessive deformations."

Do you know if this applies to a wheel coming off, which was checked for correct torque settings before we left our site 15 miles earlier?

Many thanks.