A subsea hydrocarbon flow compression system (100) for receiving a hydrocarbon stream from at least one upstream flowline (102, 104) and supplying the hydrocarbon stream to at least one downstream flowline (106, 108) at an increased pressure, wherein the compression system comprises first and second compressor trains (110a, 110b), wherein each compressor train comprises an inlet port (112a, 112b) which is connectable to the at least one upstream flowline (102, 104); an outlet port (114a, 114b) which is connectable to the at least one downstream flowline (106, 108); a conditioning unit (116a, 116b) which is connected to the inlet port via a first flowline (118a, 118b); and a first flow path for the hydrocarbon fluid comprising a compressor (120a, 120b), which compressor is connected to the conditioning unit via a second flowline (122a, 122b) and to the outlet port via a third flowline (124a, 124b), wherein a controllable first valve (126) is arranged in the third flowline of the first compressor train for controlling hydrocarbon flow from the compressor to the outlet port of the first compressor train. A controllable second valve (128) is arranged in the second flowline of the second compressor train for controlling hydrocarbon flow from the conditioning unit to the compressor of the second compressor train. The system further comprises a first cross-over flowline (130) interconnecting the third flowline of the first compressor train upstream of the first valve and the second flowline of the second compressor train downstream of the second valve, wherein a controllable first cross-over valve (132) is arranged in the first cross-over flowline for controlling hydrocarbon flow through the first cross-over flowline.