An aircraft gas turbine engine comprises a high pressure compressor driven by a high pressure turbine via a high pressure shaft, a first combustor provided downstream of the high pressure compressor and upstream of the high pressure turbine, a low pressure compressor driven by a low pressure turbine via a low pressure shaft, the low pressure compressor being configured to provide air to the high pressure compressor and to a bypass flow. The low pressure turbine comprises at least first and second turbine stages. The engine further comprises a second combustor provided downstream of the first stage of the low pressure turbine and upstream of the second stage of the low pressure turbine. The engine comprises a shaft coupling arrangement configured to transfer power between the high and low pressure shafts.