Herrmann settled in Kenya and built a life there as a businessman, running a resort hotel on the coast at Malindi and a car dealership in Nairobi. His adopted home country formed the backdrop for his most significant motorsport achievements, and he became closely associated with the Safari Rally — one of the most demanding and unpredictable events in international rally competition.
Herrmann made his mark at the Safari Rally across a period spanning more than a decade. In 1968 he entered with a Porsche 911 but retired from the event. The following year, 1969, he drove a Datsun P510 to fifth place — a strong result on an event notorious for attrition. He then converted that form into outright victories.
When the Safari Rally entered the International Championship for Manufacturers (IMC), Herrmann won it in 1970 driving a Datsun 1600 SSS and again in 1971 with a Datsun 240Z. These back-to-back wins on his home terrain represented the peak of his rally career and established him as one of the most capable drivers on African roads.
In 1972 he took the 240Z to fifth place, continuing his impressive record at the event. After the World Rally Championship was established in 1973, Herrmann competed at the Safari Rally with the 240Z but retired due to a broken head gasket. The 1974 Safari Rally saw him enter in a Porsche Carrera RS, again retiring with an engine problem.
He continued returning to the Safari Rally through the following decade. In 1976 he drove an Opel Kadett GT/E, and in 1982 and 1983 he co-drove for Swiss driver Hanspeter Ruedin in a Mitsubishi Lancer Turbo — the pair retiring in 1982 and placing thirteenth in 1983. In 1984 and 1985 he returned as a driver in his own right in a Mitsubishi Starion Turbo, retiring on both occasions.
Beyond his home event, Herrmann's international WRC results were modest. His only finish outside the Safari Rally at an IMC or WRC round was a seventeenth place at the 1971 RAC Rally. He competed at the 1973 Press-on-Regardless Rally in North America, finishing fourteenth in a Subaru GL.
In 1973 he won the non-championship Rallye Côte d'Ivoire, another African event where his experience on rough, unpredictable terrain was an asset.
Edgar Herrmann's consecutive Safari Rally victories in 1970 and 1971 place him among the notable winners of what was considered one of the world's toughest rallies — a marathon event over thousands of kilometres of African bush tracks where mechanical survival was as important as pace. His results were achieved with Japanese machinery at a time when European manufacturers dominated international competition, reflecting both his car preparation skills and his intimate knowledge of Kenyan roads.