By introducing this, we could dramatically reduce the number of accidents that learner drivers are involved in by ensuring that there is a minimum standard to which all of our road users are compliant with.
A 'Compulsory Basic Training' course should be introduced for learner drivers of all types of vehicle, not just categories A and P. As per the present CBT for said categories, it should consist of an off road element to ensure that the learner driver is familiar with the essentials of how to handle a car before being let loose on Britain's roads. At present, it is theoretically possible to get a provisional license, get insured and into a car, all be it with a full license holder over 18yearsofage, without knowing how responsive the controls are or even necessarily what they do (as daft as this sounds, such people are out there!). I do not suggest, however, that this should replace the requirement for a license holder over 18yearsofage to be present with the learner driver.
Potentially this could also be a use for the dozens of closed RAF airfields languishing around the country too. The perimeter roads, former accommodation areas, taxiways and runways are absolutely ideal for the task!