His first deployment was at the Swedish embassy in London where he directly experienced the outbreak of World War II and the subsequent German bombings.
[2] Hagen then spent two years working at the ministry's headquarters in Stockholm before taking over the position as ambassador of Egypt in Cairo, where he also oversaw Sudan and Somalia.
In Egypt, Hagen experienced several turbulent incidents such as the Six-Day War and the assassination of prime minister Wasfi al-Tal of Jordan.
After ending his assignment at Volvo, Hagen began penning his memoirs which resulted in the book Ett liv i krig och fred (A life in war and peace) which was published in 2000.
In June 1995 Hagen appeared in the BBC documentary Myths and memories of World War 2 discussing the potential peace-treaty between England and Germany in 1940.