A gas turbine fuel supply method and arrangement is provided. The method of controlling a supply of a fuel to a combustor of a gas turbine having a compressor upstream of the combustor, the method including: supplying the fuel to the combustor; obtaining an inlet air pressure (PT7) at a compressor inlet; obtaining an inlet air temperature (Tinlet) at the compressor inlet; obtaining an outlet air pressure (PT8) at a compressor outlet; estimating a heat input (HIengmodel, HIexpected) of the fuel supplied to the combustor based on the inlet air pressure (PT7), the inlet air temperature (Tinlet) and the outlet air pressure (PT8); comparing the estimated heat input (HIengmodel, HIexpected) with a demanded heat input (FFDEM) to derive an error signal; and controlling a fuel valve regulating the supply of the fuel to the combustor based on the error signal.