Rachel Willmott clinched her fifth British crown and Tom Pashley became a national champion for the first time at Manchester.
Rachel (Horsham) retained the under-15s title to add to her two triumphs at under-13s and one at under-17s.
She stormed to glory without dropping a game, whitewashing Monique Shaheed (Leicestershire) 3-0 in the final after dropping just two points in the semi against Victoria Lust (Bedfordshire), the British under-13s champion.
Mike Harris, who coaches both champions, said: "Rachel won at a canter. She was relentless. Rachel is slight but even the girls who are physically bigger can't get to her. She returns their shots with interest. She just wants to win. She fights for everything."
Rachel, a pupil at Farlington school, said: "The thrill is just as exciting as any of my other national titles.
"I don't think about losing. I have the killer instinct. It was a great event for Sussex."
Top seed Pashley (Dunnings Mill, East Grinstead) beat Ollie Pett (Storrington) 3-1 in a hard-fought all-Sussex final.
Pashley, who attends Oathall (Haywards Heath), said: "I was emotional at the end. It was so hard and such a relief. It feels exciting to be a national champion."
He dismissed Neil Cordell (Yorkshire), another under-13s' champion, 3-0 in the semis.
Pett, seeded five to eight, upset third/fourth favourite Darren Healey (Somerset) 3-2 and second seed Jim Bristow (Devon) 3-1 to make the final.
Harris said: "I told Tom before it started that it would be the hardest thing he had ever tried to do, even though he was favourite and had beaten the same players before.
"It's all very well winning the Chichester Junior Open, but going for a national title is a lot different. It's like Tim Henman going for Wimbledon compared to a regular tour event.
"It was hard. The final was nip and tuck and Tom was on the floor in tears. He couldn't believe it."
Susie Pierrepont, from Brighton and Hove, was defeated 3-1 by British No.1 Alison Walters (Middlesex) in the girls' under-19s final after taking the first game 9-2. It followed a 3-0 victory for the Varndean pupil over Kirsty McPhee (Yorkshire) in the last four.
Harris said: "Susie was gutted. It was her last chance to win at under-19s. But at least she managed a national title win at under-12s and can aim for glory in the European Under-19s Championships next month as part of the England team."
Alex Crouch (Hellingly) made the quarter-finals of the under-19s.
Katie Hanley (Middleton) made the quarter-finals of the under-15s.
Harris believes it can get better for Sussex.
He said: "This is a big deal for Sussex. What the players achieved is awesome and will act as an inspiration to other youngsters in the county.
"We've got some good coaches in Sussex, including myself and Graham Stevenson, who also coaches Tom, but we need more."
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