A gas turbine engine may include a high pressure compressor coupled to a high pressure turbine by a high pressure shaft, a core combustor located downstream of the high pressure compressor and upstream of the high pressure turbine, and a low pressure compressor provided upstream of the high pressure compressor. The low pressure compressor may be configured to direct core airflow to the high pressure compressor and first bypass airflow which bypasses the high pressure compressor, core combustor and high pressure turbine through a first bypass duct. The engine may further include a mixer downstream of the high pressure turbine and low pressure compressor, the mixer being configured to mix the core and first bypass airflows. The engine also may include a re-heat combustor configured to combust fuel with both core airflow and first bypass airflow. A low pressure turbine may be provided downstream of the re-heat combustor and coupled to the low pressure compressor (14) by a low pressure shaft, the low pressure and high pressure shafts being independently rotatable. A shaft power transfer arrangement may be provided, which is configured to selectively transfer power between the low pressure and high pressure shafts.