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Hello, I hope the following assist you.
Without doubt you need to drain the tank, clean the fuel lines and replace the fuel filter. The car may run OK with the 10% of petrol in it or be slightly noisier but it's the long term damage that occurs when petrol is in the fuel. Diesel is an oil it lubricates the fuel pump and injectors, petrol is a solvent it washes the diesel away causing a lack of lubrication, the effect of this may not be immediately noticeable but in few thousand miles the damage that can be caused will start to show.
I hope this helps but if you have more questions regarding this let me know and I'll reply as soon as I'm able to.