Please read the other posts in the thread. Petrol in the diesel fuel cannot cause uncontrolled revving. Higher concentrations will result in detonation and potential damage but ratios could be well above 50% for any problem. Lubrication of the injector pump is another potential issue and I would add half a pint of lube oil to the tank if ratios went above 50% petrol, just to be safe.
Huw