In September 1939 World War II began, and the tanker markets became very strong. Even though sailing under a neutral flag the "Viking Tanker Company" vessels were able to trade as they followed British regulations. Næss travelled to Norway in April 1940, as he had been requested by the British Ministry of Trade to contact Norwegian shipowners that did not fully support the blockade of Germany. He would also meet his colleagues in Sandefjord, Johan Rasmussen and Torger Moe. Næss managed to have a meeting on 8 April 1940 with the Norwegian Foreign Minister, Halvdan Koht and woke up the day after, 9 April with the German invasion of Oslo, seeing the German transport planes landing at the Fornebu airport from his brother Arne Næss's house in Holmenkollen. Næss was pessimistic about Norway's chances towards the German invasion and escaped Oslo on 10 April, heading westwards by air. The journey would be by train, air, car and small boats and he finally ended up in Ålesund where he volunteered as an interpreter for the British Expeditionary Force. On the way he was twice locked up by Norwegian police, suspecting him of being a spy. After a few weeks in Ålesund the British forces had to withdraw and Næss followed them back to Britain.