I RECENTLY overheard a conversation in which one person stated to another: ‘Yes I can drive your car - I have fully comprehensive insurance so if it gets damaged it's ok'.

It illustrated a modern myth in in which drivers who are fully comp may sometimes have a firm belief that they can drive someone else's vehicle without risk.

Churchill Car Insurance has been exploring this worrying trend and have come up with figures thatreveal millions of motorists on Britain's roads could be driving with invalid insurance, or far lower cover than they believe to be in place.

Over a third of people with a UK driving licence questioned think that if they have a fully comprehensive car insurance policy they can drive any vehicle with the same level of cover. This figure rises to almost half of those aged 18-34 years old.

However, almost no insurers offer ‘open' cover for driving other cars, which would allow all licence holders to drive cars not listed on their policy. As a result, many motorists risk travelling thousands of miles in the cars of friends, family members or colleagues without insurance.

A third of licence holders who took part in the research said that said they would assume their cover extends to other vehicles believe a fully comprehensive policy allows them to drive another vehicle with no restrictions whatsoever. Less than a quarter questioned would inform their insurer if they wanted to drive another vehicle.

Worryingly just 40 per cent have ever checked whether there are exclusions that would prevent them from driving someone else's car. This lack of awareness means millions of drivers could be getting behind the wheel and not be covered in the event of an accident.

The research reveals just 12 per cent of motorists who believe they are covered to drive any car understand that it is likely to be for a limited time period and just 16 per cent think it would be restricted to emergency situations only.

Driving other cars cover, which often only extends to third parties, is only intended by insurers to be used for a very small proportion of time during a policy year. The intention of any cover provided is to ensure third parties have some degree of legal protection if the insured customer has to drive a car in an emergency, such as the owner of the vehicle being taken ill unexpectedly.

Rob Miles, director of Motor at Churchill Insurance, said: ‘Fully comprehensive insurance does not cover every driver in every situation and it's worrying to see that so few motorists understand this.'