A method of utilising a flameless combustor system, wherein the flameless combustor system comprises: a combustion chamber extending longitudinally through which a high temperature oxidising agent flows in the longitudinal direction from an inlet to an outlet , at least two fuel lines ; wherein at least one fuel injection pipeline in fluid communication with a first of the at least two fuel lines extends through a wall of the combustion chamber, wherein each fuel injection pipeline contains at least one fuel injector for injecting fuel into the combustion chamber; wherein at least one of the at least one fuel injection pipelines extends through the wall of the combustion chamber, across the interior of the combustion chamber to an opposite wall of the combustion chamber, and through the opposite wall, such that the fuel injection pipeline is in fluid communication with both the first of the at least two fuel lines and a second of the at least two fuel lines, and the method further comprising: providing the high temperature oxidising agent through the inlet and admitting fuel into the at least two fuel lines such that the fuel will pass into the at least one fuel injection pipelines and be expelled through the at least one fuel injectors, with the velocity and pressure of the high temperature oxidising agent and fuel selected so as to establish the same air-fuel ratio at each of the at least one fuel injectors, and wherein the temperature of the high-temperature oxidising agent is above the auto-ignition point of the fuel. a combustion chamber extending longitudinally through which a high temperature oxidising agent flows in the longitudinal direction from an inlet to an outlet , at least two fuel lines ; wherein at least one fuel injection pipeline in fluid communication with a first of the at least two fuel lines extends through a wall of the combustion chamber, wherein each fuel injection pipeline contains at least one fuel injector for injecting fuel into the combustion chamber; wherein at least one of the at least one fuel injection pipelines extends through the wall of the combustion chamber, across the interior of the combustion chamber to an opposite wall of the combustion chamber, and through the opposite wall, such that the fuel injection pipeline is in fluid communication with both the first of the at least two fuel lines and a second of the at least two fuel lines, and the method further comprising: providing the high temperature oxidising agent through the inlet and admitting fuel into the at least two fuel lines such that the fuel will pass into the at least one fuel injection pipelines and be expelled through the at least one fuel injectors, with the velocity and pressure of the high temperature oxidising agent and fuel selected so as to establish the same air-fuel ratio at each of the at least one fuel injectors, and wherein the temperature of the high-temperature oxidising agent is above the auto-ignition point of the fuel. providing the high temperature oxidising agent through the inlet and admitting fuel into the at least two fuel lines such that the fuel will pass into the at least one fuel injection pipelines and be expelled through the at least one fuel injectors, with the velocity and pressure of the high temperature oxidising agent and fuel selected so as to establish the same air-fuel ratio at each of the at least one fuel injectors, and wherein the temperature of the high-temperature oxidising agent is above the auto-ignition point of the fuel. <EOS>