A gas turbine engine includes a first flow passage and a main combustion arrangement in the first flow passage. The engine further includes a second flow passage and a first catalytic combustion arrangement in the second flow passage, wherein the second flow passage can communicate with the first flow passage at at least one upstream passage junction upstream of the main combustion arrangement and upstream of the first catalytic combustion arrangement, and the second flow passage can communicate with the first flow passage at at least one downstream passage junction downstream of the main combustion arrangement and downstream of the first catalytic combustion arrangement.