Jaguar was able to get an unofficial practice in May on the full track in an unrelated event and Tony Rolt took the prototype D-type round fully 5 seconds faster than Alberto Ascari's lap record from the previous year in the Indy-engined Ferrari. In the official practice, all three works cars recorded identical times. and they and the Ferraris were a step up from the rest of the field. Overall, the Jaguars had better handling, disc brakes and were faster (Moss was timed at 154.44 mph/278 km/h over the flying kilometre, giving a huge 20 km/h advantage), but the Ferrari had superior power and acceleration. The supercharged Aston Martin, the Lagonda, and the Porsches were also impressively quick.