I saw the 5th gear vid but was a little stupid to put it mildly.
This is from the AA website:
More importantly, putting petrol into a diesel tank causes more damage.
That’s because diesel acts as a lubricant, helping the fuel pump to do its job. Petrol, on the other hand, causes the reverse to happen: it actually increases friction between parts in the diesel engine. And that’s never good news for an engine. So the more petrol that gets pumped through your diesel fuel system, the more damage it will do.
Common rail (or HDi) diesel engines are particularly susceptible to damage from misfuelling. If the damage is extensive, you could be looking at new fuel pumps, injectors, pipes, filters, fuel tank – or even a whole new replacement engine. Not good.