Method of controlling the speed of the in-feed system and the speed of the first moving grate of a combustion facility, said combustion facility comprising an in-feed system feeding fuel to a number of moving grates on which the fuel is fed forward and subjected to successive drying, ignition, combustion and outburning, primary air for the combustion being supplied from beneath the grates and through the layer of fuel on the grates, said method comprising - calculating a coefficient of resistance ( ζpv) for the airflow through the combustion grates and fuel, - controlling the speed of the in-feed system, - controlling the speed of the first moving grate of the combustion facility based on the coefficient of resistance ( ζpv), - providing an estimation ( Fpv) of the position of the flame front by image analysis of a camera image of the combustion zone, and - using said estimated position ( Fpv) of the flame front for the control of the speed of the first moving grate, characterised by - controlling the speed of the in-feed system based on the coefficient of resistance ( ζpv), - using said estimated position ( Fpv) of the flame front to provide a correction of the control based on the coefficient of resistance ( ζpv) of the speed of the in-feed system and the speed of the first moving grate; - whereby the correction to the control based on the coefficient of resistance ( ζpv) is performed by any of - a feedforward introduction of the estimated position ( Fpv) of the flame front, whereby a set point of a coefficient of resistance controller is additively corrected by a flame front control signal, - a scaling introduction of the estimated position ( Fpv) of the flame front, whereby a set point of a coefficient of resistance controller is scaled by a flame front control signal, - a gain scaling introduction of the estimated position ( Fpv) of the flame front, whereby a flame front control signal directly scales a set point to a feeding control system. - calculating a coefficient of resistance ( ζpv) for the airflow through the combustion grates and fuel, - controlling the speed of the in-feed system, - controlling the speed of the first moving grate of the combustion facility based on the coefficient of resistance ( ζpv), - providing an estimation ( Fpv) of the position of the flame front by image analysis of a camera image of the combustion zone, and - using said estimated position ( Fpv) of the flame front for the control of the speed of the first moving grate, - controlling the speed of the in-feed system based on the coefficient of resistance ( ζpv), - using said estimated position ( Fpv) of the flame front to provide a correction of the control based on the coefficient of resistance ( ζpv) of the speed of the in-feed system and the speed of the first moving grate; - whereby the correction to the control based on the coefficient of resistance ( ζpv) is performed by any of - a feedforward introduction of the estimated position ( Fpv) of the flame front, whereby a set point of a coefficient of resistance controller is additively corrected by a flame front control signal, - a scaling introduction of the estimated position ( Fpv) of the flame front, whereby a set point of a coefficient of resistance controller is scaled by a flame front control signal, - a gain scaling introduction of the estimated position ( Fpv) of the flame front, whereby a flame front control signal directly scales a set point to a feeding control system. - a feedforward introduction of the estimated position ( Fpv) of the flame front, whereby a set point of a coefficient of resistance controller is additively corrected by a flame front control signal, - a scaling introduction of the estimated position ( Fpv) of the flame front, whereby a set point of a coefficient of resistance controller is scaled by a flame front control signal, - a gain scaling introduction of the estimated position ( Fpv) of the flame front, whereby a flame front control signal directly scales a set point to a feeding control system.