Engine valve control during cylinder reactivation

A method of controlling an internal combustion engine having a plurality of cylinders, for switching between a first mode in which at least one cylinder is deactivated by closing its inlet and exhaust valves and a second mode in which a previously deactivated cylinder is active. The switching is effected by cycling the engine while operating the inlet valves to admit air into the deactivated cylinder so as to raise the temperature of the cylinder prior to introducing fuel to activate the cylinder. The number of cycles in which air but no fuel is admitted into the cylinder may be set in dependence upon input from a demand pedal. Both inlet and exhaust valves may be operated when switching from the first mode to the second mode prior to the introduction of fuel.