Professor Donner qualified for the bar in Finland (vicehäradshövding) in 1977 and served on the bench as deputy judge and acting chief judge of the City Court of Mariehamn for several years in the late 1970’s. Professor Donner served the Sally Shipping group for 12 years, advancing from chief legal counsel and company secretary to deputy managing director with responsibility for the legal affairs of the group, which owned oil tankers, had ferry operations in Scandinavia and the United Kingdom, and cruise operations in the Caribbean.
After the Sally Group he was managing director for Delfin Cruises Ltd. in Finland, operating cruises in the Baltic. He ran his own law and management consultancy firm for a few years after leaving Delfin Cruises Ltd. Throughout his early career he taught maritime law at the Maritime Academy of Åland, held numerous non-executive positions on boards of directors of shipping and insurance companies, and served as an elected public office at the local level.
Since January 1995 Professor Donner has been at the World Maritime University in Malmö, Sweden, first as Associate Professor in Shipping Management and currently as Associate Academic Dean. He is also Programme Director for the Postgraduate Diploma in Marine Insurance course offered by distance learning.