'Lark Durham' was a British operation by the Special Operations Executive to establish radio contact, reorganise 'Lark', and enlarge the 'Durham' propaganda organisation in German-occupied Norway (March 1944/spring 1945).
The three-man party, comprising E. Gjems-Onstad, I. Gausland and H. Larsen, arrived overland from Stockholm in neutral Sweden, and Gausland went to Trondheim in January to rebuild contacts after a wave of arrests. Gjems-Onstad followed in March to take over the leadership and act as radio operator. Gjems-Onstad built up local groups, returned to Stockholm in June, and came back to Trondheim in August with a new radio operator, E. Løkse. Løkse was arrested, and Gjems-Onstad returned to Stockholm before coming back once more for 'Durham' activities. Eventually F. Beichman, followed by T. Bjørnas and A. Wisloff, joined him as radio operators. In 1945 some railway sabotage was undertaken before Gjems-Onstad returned to Stockholm for the last time.