Chichester High pupil Charlotte Browning became the first Sussex athlete to win the under-13s title.
She won the title when she romped home through the wind and rain at the Inter-County Cross Country Championships in Nottingham.
She said: "Conditions were not nice and I did not set out to run away from the field. In fact, I was lying third as we topped the first hill.
"But I just found my own pace and no one wanted to stay with me. I finished 20 seconds clear and felt quite comfortable. I will now be looking to the National Championships and the All England Schools' Championships."
Charlotte has been unbeaten since finishing fourth in the National Cross Country Championships at Stowe last March when she was fourth.
She is the first county winner at the Inter Counties since Joe Forshew, another Chichester athlete, claimed the under-17s crown in 1994.
Sarah-Jane Pickett, a Horsham Club runner, won the under-13s title representing Surrey. three years ago.
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