Under his leadership Verdens Gang became the main publication for the Liberal Party, and a modern newspaper of high standard.

[3] Thommessen frequently corresponded with the writer Bjørnstjerne Bjørnson at this time,[4] and was also a friend of Lars Holst, Oda Krohg, Mathilde Schjøtt as well as Maren, Ossian and Ernst Sars.

Around the turn of the century he instead advocated a bourgeois coalition in light of the growing socialist movement.

The incidents leading to his resignation, a conflict with lawyer and share owner Ole Madsen, made him a legend.

Tidens Tegn soon became one of the country's most important and largest newspapers, and many important cultural personalities were among the contributors, including Sven Elvestad, Olaf Bull, Hans E. Kinck, Herman Wildenvey, Nils Collett Vogt and Selma Lagerlöf.

He was skeptic to the Norwegian Parliament, and advocated a strong bourgeois leadership as a leading member of Fedrelandslaget.