In previous years they had made the semi-finals three times and never failed to reach the knock-out stages. But, having gone into the tournament on the back of triumphs in the Marches and Llandovery competitions, they turned on the style to become the first Welsh team to win the prestigious Open Under 18 title since St Cyre's, Penarth, in 1995.
"We were in the tough side of the draw and Whitgift gave us a really tough time but we did enough to get over the line.It's been 10 years in the making and I'm just so proud of the boys," said Sir Gar head of rugby Euros Evans.
"It's been a really tough tournament but it's the pinnacle of schoolboy Sevens. The boys were challenged both physically and mentally and we're just so chuffed."
Evans' side conceded only six tries in nine games and kept their line intact in four games, including the high-pressure final. They breezed through their Group, scoring 166 points and conceding a mere 12 as they beat Adams GS 45-7, Tiffin 38-0, Greenhill 50-5 and Emanuel 33-0.
Day two was the knock-out phase and Sir Gar were determined to improve on their semi-final place the previous year. They had little trouble in overpowering Campion School, 33-0, in the Final 32, and were 35-7 winners against St Benedict's, Ealing in the Final 16 of a tournament that had 105 schools, 29 from Wales.
The quarter-final saw them face reigning champions Filton College, who they had beaten in the semi-finals of the Marches 7s, and they won 14-10 in their closest game of the tournament. That set-up a semi-final clash with Millfield, who had reached the final four thanks to a 22-17 extra-time win over Llandovery College.
The two teams had met in the final of the Marches 7s earlier in the year, when Sir Gar were 26-21 winners, and the fixture gave the Welsh side a chance to avenge their semi-final defeat in the 2009 competition at Rosslyn Park.
In the end, it turned into another routine victory with Sir Gar totally dominating as they went on to win 32-7 to reach their first Open Final. Whitgift beat Sedbergh in the semi-finals to join them and, having scored 184 points in their Group matches, they were tipped to provide a tough test.
But they failed to score a point in the final and Sir Gar picked up their third, and biggest, title of the season to join Llanelly Grammar School, Monmouth School, Llandovery College, Neath Grammar School, Neath College and St Cyre's School, Penarth, in winning the Open title
Two other Welsh schools reached finals, but failed to take titles. College Sir Gar's Under 18 women's side were one of six Welsh teams among the 24 and reached the final at their first attempt. They were 52-0 winners against Maidstone Grammar School, beat Rossall 57-0 and then Colston's 33-5 in the semi-final.
They were then beaten 29-0 by Moulton College in the final. Ysgol Dyffryn Aman, Amman Valley School, reached the last 32 before going down 28-14 to Hartpury College after winning all three Pool games against Peter Symonds' College, Christ's Hospital and The Judd School.
Ysgol Gyfun Glantaf managed seven successive victories in the Junior School Under 13 tournament. They beat St Joseph's College, Ipswich, Manchester Grammar School, Tiffin, Royal Latin School, Trinity School, Solihull School and Whitgift before facing St Benedict's of Ealing in the final and losing 24-0.