Jonathan Freedland takes the long view of pioneering invention and the trials and tribulations thereof in the form of Elon Musk's Hyperloop and Isambard Brunel's Atmospheric Rail system. Both men were driven and capable of challenging accepted engineering norms but in their two rail systems they struggled to make a break through. Elon Musk believes that his Hyperloop system can shoot passengers at breakneck speed through a vacuum tube, cutting journey times and revolutionising rail travel. Ever the coy publicist he refers to his Hyperloop as the "fifth mode of transport" after road, rail, sea and air. Brunel was convinced that steam wasn't the only way of providing cheap, efficient mass transport. Using a sealed tube in the centre of the rails to deliver vacuum propulsion, his system ran on a 20-mile section of track between Exeter and Newton Abbot and was a match for the speeds available to the best steam trains of the day. But both systems have proved more than challenging and in Brunel's case the challenges became insurmountable and the inventor's appetite for new adventures saw it fall quickly into disuse. How will Elon Musk's plans mature? Historian Colin Divall is on hand to help tell the parallel stories of these two men and their transport dreams. Producer: Tom Alban