In the final part of his documentary series, Rob Bell uncovers the extraordinary story behind what was once the longest passenger ship in the world. Designed by Victorian engineering genius Isambard Kingdom Brunel, the SS Great Britain rewrote the shipbuilding rulebook, pioneering innovations still found on almost all modern ships. Rob learns how the origins of the vast vessel lay in an off-the-cuff boast of Brunel's. Though the ship's early years were plagued by disaster, it finally met with success thanks to the Australian gold rush - and today 250,000 Australians can trace their direct ancestors to its passengers.