The high-pressure combustion duct (HPCD) is one of the CCRC's flagship test-rigs. It was tailor-made (vertically-oriented and 8-m tall) to investigate long turbulent flames at elevated pressures of up to 40 bar. Its large inner diameter of 410 mm accommodates a wide range of burner designs, allowing to study a variety of flames, from canonical jet flames to compact swirl flames typical of those found in gas turbines. The HPCD is fitted with six UV-grade windows, enabling measurements of species, temperature, and velocity using advanced laser diagnostics such as laser-induced fluorescence, Raman spectroscopy, particle imaging velocimetry, and laser-induced incandescence. The HPCD can be fueled with a wide range of combustible gases, including methane, ethane, ethylene, hydrogen, ammonia, and syngas.