depends on how you get on with speaking up in public, that sort of thing. Personally I'd plead not guilty and site the reasons above. You'll get every chance to speak up in court. Plod love to try and bully people with the "due care" charge for just about anything. It often evaporates when they realise they will have to go to court etc. It's only worth a lawyer if they have the potential to get you off, they do and it may well be worth it but the fees may well be worse than the fine if found guilty. You may get a slightly worse punishment if found guilty having pleaded not guilty but in this case I think the whole thing will evaporate once you plead "not guilty". Make sure you tell them about the diesel spill bit.