rover 75 cutting out ?

my rover 75 has been running well. but last week i run out of petrol. i filled it up and all was well. but on my way to leiston on the a12 my car brock down. all the warning lights came on. and the car went dead. lost all power to the engine. i called the green flage to come out. it was an hour untill they turned up. he put the key in and it started first time. i then went to leiston all was ok. but on coming home the car did the same thing. the roads were not wet. please help