Short answer: Meeting the legal minimum does not prove the policy conditions are met. Check the current government rules and the policy wording as two separate sources.
Legal minimum
Use the official rules for the relevant UK jurisdiction. They cover matters such as the supervisor’s age, licence history, eyesight, use of a mobile phone and the learner’s display of plates.
Policy conditions
The insurer may require a higher supervisor age, longer licence history, a particular licence jurisdiction, residence criteria or other restrictions. A breach can affect cover even if the road-traffic supervision minimum was met.
A repeatable check
Before practice, record the supervisor’s age, licence type, licence start date and whether they are insured to drive if needed. Recheck after any policy, vehicle or supervisor change.