A combined cycle heat engine (10). The engine (10) comprises a first gas turbine engine (11) comprising a first air compressor system (14), a first combustion system (16) and a first turbine system (18) and a second gas turbine engine (32) comprising a second air compression system (36), a second turbine system (40), and a heat exchanger (38) configured to transfer heat from an exhaust (24) of the first turbine system (18) to compressed air from the second air compressor (36). The second gas turbine engine (32) comprises a second combustion system (20) downstream of the heat exchanger (38) and upstream of the second turbine system (40).