Brighton under-12s are on their way to Twickenham for the second year running.
They came through the qualifying event at the Gullivers Festival to book their place on May 30.
Captain Harry Leonard was the hero in the deciding match against Richmond at Nottingham University.
The scrum half, from Brighton College, was sick on the pitch after being accidentally kicked in the stomach but recovered to score the only try of the match.
It avenged a 5-0 defeat by the Surrey club in last season's competition.
Victory over Richmond means Brighton qualify for the semi-finals proper of the event, where they will face Blackheath.
Brighton were the only Sussex representatives in the two-day qualifying competition, which comprised 106 teams from all over the country in six different age groups.
They beat Northampton Old Scouts and Doncaster by the maximum 30-0 margin, Rugby Lions 20-5 and drew 0-0 with Wiltshire champions Salisbury.
The other try scorers were Craig Holland (4), Chris Byrne (3), Darion Naylor, Will Duffel and George Taylor (2), James Kinsella, Thomas Chang and Leonard.
Blackheath were the only team to beat Brighton, winning their group encounter 10-0.
Brighton drew 0-0 in the plate final against Lincoln last year but coach Neil Thomas said: "This is a greater achievement than that.
"We are through to the semi-finals of the whole competition and we had to do it the hard way. The boys ran favourites Blackheath close and then had to lift themselves against Richmond."
Haywards Heath under-12s, triumphed at the Cambridge Minis Festival.
They won all five of their matches and did not concede a try. They beat Bury St. Edmunds 35-0, Huntingdon 20-0, Bedford 10-0, Cambridge 20-0 and Hertford 10-0.
Heath under-12s: William Fell, George Heron, Dan Harris, James Tyas, Patrick Lamb, Robbie Thomson, James Parr, Adam Davis, Jake Henry, William Fraser, Jake Baldwin, Freddie Duff, James Brown, Cameron Simcock, Matthew Walsh, Alex Esson.
Haywards Heath under-11s were runners-up to Bedford.
They overcame Bury 15-0, Huntingdon 25-0 and Hertfordshire 10-0, drew 0-0 against third-placed Cambridge and lost 10-0 to Bedford.
Heath under-11s squad (with try scorers): Heath squad and try scorers: Michael Brook, George Clutton, Dominic Fry (five), Kieron Martin, Will Martin, David McClure, Michael McCullough, Olliver Meredith (two), Kitt Onyett (one), James Pearce, Harry Preston Bell, Josh Spuyman (two), George Wilkes (one), Jack Wrench, Anton Wright.
Haywards Heath under-tens finished fifth out of eight teams.
They drew 5-5 with Bury, defeated Hertfordshire 10--0 and lost 20-0 to Cambridge A.
Lewes under-17s/18s suffered two defeats on a tour to Lille, France.
They were beaten 42-0 by Arras who contained two under-18 internationals and several provincial representative players.
Injury-hit Lewes lost their second game 33-0 to Valenciennes.
Lewes under-eights won the Uckfield Festival, beating Heathfield 15-10 in the final after defeating Crowborough 25-5 in the semi-final.
The under-nines pipped Crowborough 5-0 in the final.
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