01/10/2008 00:01. One word sums up the Q7: epic . Audi's flagship 4x4 is already one of the biggest in its class and now it boasts an equally colossal engine: a 493bhp, 5.9-litre diesel.

Its performance is devastating, as you would expect. From the lights the 2.7-tonne Q7 launches into the horizon, passing the benchmark 62mph in just 5.5 seconds and slamming into its 155mph limiter in an alarmingly short space of time.

So this is the most powerful diesel passenger car ever, Audi's engineers say. They claim that the Q7's twin-turbo V12 has direct lineage to Audi's Le Mans-winning R10... // Channel 4 News