A transmission system for a vehicle, the system comprising: a. a primary input shaft for receiving drive from a primary vehicle drive motor, b. a secondary input shaft for receiving drive from a secondary vehicle drive motor; c. an output shaft for connection to drive a final drive unit; d. a multi-speed gearbox that can connect the primary input shaft to the output shaft at one of a plurality of gear ratios; e. input selection means including a gear train (3 rd) comprising an input shaft gear mounted on the primary input shaft, meshing with an output shaft gear mounted on the output shaft, a first selector for selectively connecting or disconnecting the input shaft gear and the primary input shaft, and a second selector for selectively connecting or disconnecting the output shaft gear and the output shaft; f. a spur gear provided on the secondary input shaft, the spur gear directly or indirectly meshing with said gear train (3 rd); g. a drive gear mounted on the primary input shaft for transmitting drive from the primary vehicle drive motor to the primary input shaft, and h. a selector clutch for selectively connecting or disconnecting the drive gear and the primary input shaft; in which the input selection means, in a first mode, connects the secondary input shaft to the output shaft by disconnecting the input shaft gear from the primary input shaft and connecting the output shaft gear to the output shaft to transmit drive from the secondary vehicle drive motor to the final drive unit via the output shaft and, in a second mode, connects the secondary input shaft to the primary input shaft by connecting said input shaft gear to the primary input shaft and disconnecting said output shaft gear from the output shaft to transmit drive from the secondary vehicle drive motor to the final drive unit via the primary input shaft, the gearbox and the output shaft. a. a primary input shaft for receiving drive from a primary vehicle drive motor, b. a secondary input shaft for receiving drive from a secondary vehicle drive motor; c. an output shaft for connection to drive a final drive unit; d. a multi-speed gearbox that can connect the primary input shaft to the output shaft at one of a plurality of gear ratios; e. input selection means including a gear train (3 rd) comprising an input shaft gear mounted on the primary input shaft, meshing with an output shaft gear mounted on the output shaft, a first selector for selectively connecting or disconnecting the input shaft gear and the primary input shaft, and a second selector for selectively connecting or disconnecting the output shaft gear and the output shaft; f. a spur gear provided on the secondary input shaft, the spur gear directly or indirectly meshing with said gear train (3 rd); g. a drive gear mounted on the primary input shaft for transmitting drive from the primary vehicle drive motor to the primary input shaft, and h. a selector clutch for selectively connecting or disconnecting the drive gear and the primary input shaft; in which the input selection means, in a first mode, connects the secondary input shaft to the output shaft by disconnecting the input shaft gear from the primary input shaft and connecting the output shaft gear to the output shaft to transmit drive from the secondary vehicle drive motor to the final drive unit via the output shaft and, in a second mode, connects the secondary input shaft to the primary input shaft by connecting said input shaft gear to the primary input shaft and disconnecting said output shaft gear from the output shaft to transmit drive from the secondary vehicle drive motor to the final drive unit via the primary input shaft, the gearbox and the output shaft.