As a full car license holder of many years, I am allowed by law to sit in the passenger seat of a car driven by a learner driver, assuming they are insured to drive that car, etc. But what is the situation if I am not insured to drive it, and furthermore I am not a car owner or policy holder where I usually would be allowed to drive a car not owned by me but covered for third party only.

Consider the situation if a problem arises and the learner is not able to continue driving no matter how temporally. I would normally take over the driving, but what now?