A method of operating an internal combustion engine having at least one combustion chamber and an actuator disposed therein being arranged to drive an output shaft of the engine, the method comprising: 5 (i) injecting a water containing fuel into the combustion chamber; (ii) flash boiling the water-containing fuel to form water vapour within the combustion chamber; (iii) thermolyzing the water vapour to form hydrogen gas and oxygen gas; and (iv) combusting the hydrogen gas to drive the actuator within the combustion chamber to 10 thereby drive the connected output shaft of the combustion engine.