INsurers refusing to insure nanny on Employers car - anyone managed it?

[TwelveLeggedWalk]

My nanny shares her car with her husband, and it's not possible for her to have her car every day at the moment. I - ignorantly - said I'd look into putting her on our insurance, not expecting it to be a problem.
Our insurers are flatly refusing, and the lowest quote I've had is #1300. The next one was #4000. My nanny is nearly 30, has no claims or accidents, and the car is over 10 years old, so clearly this is insane.
Has anyone got a nanny driving on their car insurance for less than the price of a new car?

How old is your nanny, how long has she been driving, what’s the car?
I’ve lots of experience with nannies/au pairs on my insurance but it’s only affordable if they’re over 22, have been driving for more than 3 years and it’s a smallish car.

Seems insane

I’ve always been on employers car and usually not more then few hundred tops

I'm having a similar issue. Hope you find a solution. Am following

Sorry OP, I've just seen that you've put how old your nanny is already.

Try admiral.

Try marmalade - you can buy insurance just for a specific day or time period.