Harris took gold in the women’s 100m hurdles in a time of 14.08 seconds.
The Plymouth athlete came through strongly in the second half of the race to overtake England South athlete Mallory Cluley, who had made a storming start. Both athletes are ranked in the UK’s top five for the under-20 sprint hurdles.
The Welsh International saw England Midlands, England South, England North, Wales, Scotland, North Ireland, Guernsey and Welsh Students compete against each other in 35 events at under-20 level.
Cornwall’s Grace Brock, who recently competed at the European Under-20 Championships in Sweden, was among the other winners on the night.
Harris earned her representative selection after winning the 100m hurdles in 12.93 seconds at the Midlands Championships, which now incorporate the South West Counties. She also ran in the 4x100m relay on Wednesday night but England Midlands were disqualified.
Harris also recently won a silver medal at the English Schools’ Track & Field Championships in Birmingham.