"The general rule is that car insurance ties to the car itself, not the owner or driver. The policy covers a person driving the vehicle under your permission. Sale of vehicle implies consent, meaning that the buyer can freely drive under your insurance without the need to file for their own.
Continuing to pay the insurance premium not only means you’re wasting money, but it also puts you at risk of ruining your insurance score. If the new owner gets involved in a car crash, the incident will be logged into your record, and you will have to pay for deductibles and excess costs not covered by the policy."
https://www.jdpower.com/cars/shopping-guides/when-to-cancel-car-insurance-after-selling-a-car
"When should I cancel if I sell my car?
Immediately. If you no longer own the car and you’re not replacing it, there is no point paying for cover you don’t need.
Failure to cancel could also result in a claim against your insurance if the new owner has an accident."
https://www.moneysupermarket.com/car-insurance/cancelling-car-insurance/