car insurance

[sacc]

if i insure a car in my workmates name who only has a provisional licence and put me down as a named driver with a full licence , he gets caught driving on his own or on motorway with me as a passenger am i liable

[Dudemcc]

If it is just to 'sit in' while he learns you don't need insurance, but he must be insured and declare he is a learner.
If he gets caught on his own, only he will get prosecuted, and strung up from the nearest lamppost hopefully.
If he commits any offence, with you in the vehicle, you both get prosecuted.
You will be prosecuted, if you do any of the things your are not supposed to do if you were driving whilst you are 'sitting in', smoking, eating, being over the drink limit, as you are classed as being in charge of the vehicle.
Furthermore, learners aren't allowed on the motorway, whether you are in the car or not.