sunscreen whilst running - which if any?

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Total novice trying for a 10k in about a month's time. Have been doing personal training and circuits for 5 months - running a little (couple of miles) once a week for 2 months.
Can you experienced running types please suggest a good sunscreen to wear whilst hauling my sweaty self around? I have combination skin and am not sure about the combo of product, sweat and sun on my already spot prone boat race.Don't fancy skin cancer either, tho and I am gingerish...
Any suggestions re this and getting up to 10k (eek) much appreciated.

P20 is amazing... put it on 20 minutes before exposure to sun,water or exercise and it stays on the skin for over 12 hours without having to re apply. It is non greasy and non staining

Alypaly,
Thanks for this. Where would I find this miraculous stuff, please?

boots stock P20 or any good chemist

Thanks so much!