Feedback control of combustion in a gas diesel dual-fuel engine (20), based on the measured cylinder pressure, has been invented. The center of combustion and pressure rise rate is controlled by manipulating the start of diesel injection and duration of diesel injection. Measurements of transient engine operation show, that the proposed controller is able to control the center of combustion and the maximum pressure rise rate. The influence of changing intake manifold pressure, changing exhaust gas recirculation rate and changing air-fuel ratio can be compensated by the controller (10). Steady state measurements show that the gas diesel dual fuel engine reaches efficiencies around 40% with stoichiometric air-fuel ratio and diesel ratios below 5%. The results have been obtained on a slightly modified production type common-rail diesel engine with four cylinders and a displacement volume of 2 litres.