This film looks at the tough training regime undertaken by London's black cab drivers as they prepare for one of the hardest examinations they will ever take. It takes years to get to grips with the intricate road network and tangle of streets that weave their way through the heart of the capital and 70 per cent of applicants fail to finish. With repeat appearances at the Public Carriage Office to take the examination, it's a bumpy road to the coveted green badge.