On 15 September 1938, the Railton Special took the land speed record from Thunderbolt at 353.30 mph (568.58 km/h), also being the first to break the 350 mph (560 km/h) barrier. Eyston re-took the record within 24 hours (357.50 mph / 575.34 km/h), holding it again until Cobb took it a year later on 23 August 1939 at a speed of 369.70 mph (594.97 km/h).
After the Second World War further development and sponsorship by Mobil Oil led to renaming as the Railton Mobil Special. It was the first ground vehicle to break 400 mph (640 km/h) in a measured test. On 16 September 1947 John Cobb averaged 394.19 mph (634.39 km/h) (385.6 & 403.1) over the measured mile in both directions to take the world land speed record, before the American Goldenrod set a new mark for piston-engined, wheel-driven LSR cars eighteen years later.