Firemen were called to Essex University yesterday after a car had been set alight for the opening of a three-day " festival of revolution ". A student grabbed a hosepipe from a fireman, and Professor G. Barnard. of the mathematics department, struggled with the student. In the morning staff and students found barricades across the campus entrance. About 300 students are supporting the festival, which includes seminars on capitalism and black power. Students from the London School of Economics and other universities are attending. The film director M. Jean Luc Godard was at the university yesterday shooting scenes for a documentary.