Excess energy generation from renewables can be conveniently stored as hydrogen for later use as a gas turbine fuel. Also, the strategy to sequestrate CO2 from natural gas (NG) will require gas turbines to run with hydrogen-based fuels. In such scenarios, high temperature low emission combustion of hydrogen is a key requirement for the future gas turbine market. Ansaldo Energia's gas turbines featuring sequential combustion have an intrinsic advantage when it comes to fuel flexibility and in particular hydrogen-based fuels. The sequential combustion system is composed of two complementary combustion stages in series: one premix stage followed by an auto-ignited second stage overcoming the limits of traditional premix combustion systems through a highly effective extra tuning parameter, i.e., the temperature between the first and the second stage. The standard constant pressure sequential combustion (CPSC) system as applied in the GT36 engine is tested, at high pressure, demonstrating that a modified operation concept allows stable combustion with no changes in combustor hardware for the whole range of NG and hydrogen blends. It is shown that in the range from 0% to 70% (vol.) hydrogen, stable combustion is achieved at full nominal exit temperature, i.e., without any derating and thus clearly outperforming other available conventional premixed combustors. Operation between 70% and 100% is possible as well and only requires a mild reduction of the combustor exit temperature. By proving the transferability of the single-can high pressure results to the engine, this paper demonstrates the practicality of operating the Ansaldo Energia GT36 H-Class gas turbine on fuels containing unprecedented concentrations of hydrogen while maintaining excellent performance and low emissions both in terms of NOx and CO2.