Click above to watch the Audi Q7 V12 TDI take on the BMW M5

Autocar decided to find out which was faster among two unlikely bedfellows sharing one common trait: 500 horsepower. In one lane you've got the BMW M5, with ten petrol-powered cylinders. In the adjacent lane there's the Q7 V12 TDI, with twelve oil-burning cylinders. The M5 is much lighter. The Q7 has Quattro. And being England, of course it's wet. Follow the jump to see who won and by how much.