In an energy storage and recovery system for a hybrid vehicle 1, the operating ratio range of a continuously variable transmission (CVT) 10 which transfers drive between the vehicle's driveline 8 and a flywheel 9 is effectively extended by the use of an integrated starter-generator (ISG) 13 connected to the flywheel shaft 12. When there is a high mismatch of rotational speed between the propshaft 8 and the flywheel shaft 12, prior to connecting the two shafts by a clutch 11, the ISG 13 either spins up or decelerates the flywheel 9 until its speed is brought within the optimum operating range of the CVT 10. This measure reduces wear and tear on the clutch 11.