Under FIA land speed record rules, the Hydromax had to complete two runs in opposite directions on a 10-mile course in under an hour, with the average speed taken across a measured mile in each direction. The success gives JCB a second land speed record, 20 years after Green piloted the twin-engined Dieselmax to a new diesel mark of 350mph. Former RAF wing commander Green also set the outright land speed record of 763mph with Thrust SSC in 1997. FEATURE: We drive (and jump) JCB's mad Digatron monster truckThe Hydromax set the new land speed record in a dedicated sessions on Bonneville Speedway held to FIA rules. That mark did not count as an official land speed record because of differences in how the events are regulated.