All that was needed to make a mechanical energy-storage system was a good enough rotational seal, so the flywheel could spin freely inside a vacuum chamber with no air resistance.
It was Paul Collingwood who made the breakthrough, ironically with an off-cutter, to trap Kamran marginally on the line of off-stump when sweeping, while Hafeez was bowled via the inside edge and pad off Graeme Swann, who found some spin and was relatively economical.