Anyone got any experience of the insurance possibilities/options for:

(a) Visitors to the US from the UK driving a car borrowed from a US-resident family member

(b) Visitors to the UK from the US driving a car borrowed from a UK-resident family member?

a) the owner of the car contacts his insurance company and informs them that a visitor will be driving his car. Depending on the insurance in place and possibly age of visitor, this should not be an issue.

In the US insurance generally follows the car not the person so in situation a it's likely your existing auto policy would cover them if they are temporary visitors.

For the UK, call your insurance company and get temporary cover for the visiting driver(s). There will be a small premium for the period covered. In the U.S., the vehicle insurance policy can cover non-named drivers, but there may be complications depending on the state involved. As they won't have a U.S. license they may be required to get an International Driving Permit. Depends on the wording of the policy and is worth double checking with the insurance company. The stakes are much higher not being insured in the U.S.

Yeah, tried this and insurer said no way that they'd insure someone without a UK driving license and we'd have to seek a specialist insurer.

Wouldn't the borrowing driver be classed as an uninsured driver and would this have consequences if they got in an accident in regard to the claims of the other party against the policy?

If the insurance company confirms the visitor can be put onto the policy, the visitor would be an insured driver and whatever the policy covers would come into play in case of accident.

We were with Liverpool Victoria and they put both my parents on for 2 weeks who had international licenses (NZ drivers license holders). The additional premium was about £15.

This is true for Collison insurance, but I'm not sure it's true for personal liability insurance. Doesn't this follow the driver not the car, and so someone borrowing a car who did not have any liability insurance from their own policy (which would be the case for a foreign driver) would be uninsured?

You'd have to check your policy documents but my Geico policy says the following (Section I is liability):

From my USAA insurance policy

Coverage

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If I let someone borrow my vehicle, does my insurance cover them?Your policy covers anyone who has permission to use your vehicle, or reasonably believes they have permission to use it. If a driver regularly uses your vehicle for more than 60 days, you should add that driver on your policy.

Note: There is no coverage if a driver you allow to use your vehicle:

• Loans the car to another person.
• Is involved in an accident as a pedestrian.
• Is injured as a passenger.
• Rents or borrows a vehicle not on your policy.
• Acquires a new vehicle.

So the way I read it, they have the same coverage that I have.

You may have your answers already as you posted a while ago. But here is my experience. When my parents visit me in the US, my car insurance covers them with no problem. When I go to the UK, recent changes have meant that I can no longer be insured to drive their cars. I therefore need to hire a car like Budget who has speciality insurance to cover me on my US drivers license. My parents did a lot of research to see if there was anyway around it but to no avail. Such a pain.

Check your credit card. It may provide cover for you. My Chase card did and they supply a letter to present to the car rental company.