Tow Bar "MODIFICATION"

I am going to lend my caravan to my Daughter and her Husband, for a weekend away, my son in law rang his insurance company to find out if he was covered for third party in case anything happened,

This was the answer

Because he had fitted a towbar and had not told his insurance company that he had "modified" the car, he had in fact been travelling around with NO insurance and had he had an accident he would not have been covered and he had to pay £26 to add this "Modification to  his policy, if he had told them that a towbar was fitted on taking out the policy there would have been no charge,

Worth checking with you insurace company

! Are you covered third party when towing

2 Do you need to notify them of a tow bar Modification