Not enough opportunities to grow. Promotions are highly dependent on someone leaving the job and creating vacancy.
As a graduate there is always opportunity to move into a permanent role
Employment after the program is guaranteed, however, there will need to be an opportunity or position available in an existing team to join. There are progression opportunities available in most roles depending on the team. For the entry engineering position there is a roof on that role that is reached after three years, a senior role will be then required to keep progressing.