A controller for a gas turbine is arranged to supply a load L. The gas turbine includes a fuel supply arranged to supply fuel at a fuel flow rate FF to a combustor, wherein the fuel supply includes a first fuel supply and a second fuel supply. The controller is arranged to determine one or more ratios R of one or more combustor operating parameters COP respectively at the load L to respective reference combustor operating parameters COPR at a reference load LR. The controller is further arranged to control a proportion P of the fuel flow rate FF supplied via the first fuel supply based, at least in part, on the determined one or more ratios R. A gas turbine with the controller and a method controls the gas turbine.