The second half saw no drop-off in intensity as both sides traded tries. When Waikato replacement loosie and 2014 NZ Schools rep Christian Kelleher crossed at 64 minutes, Waikato had snatched a 35-34 lead.
But resilient Canterbury, who committed just three handling errors, hit back 90 seconds before no-side with a try in the right corner to wing Fraser Scott after a long, patient build-up.
Cameron converted from the sideline, capping a 12 from 12 effort by the kickers off the tee.
Canterbury's post-match chant centred around winning tryscorer Fraser Scott, in the manner of the Crusaders' old Reuben Thorne chant.
"There was a lot of preparation go in over the last three months... I'm just happy we came through," said Canterbury captain, No 8 Elia Elia, one of a clutch of players, including halfback Logan Crowley and lock Hamish Dalzell, back from last year. Gamble, who scored a second try off a lineout drive, won the DJ Graham Award for the tournament MVP off the man himself. Fittingly, Gamble is the second No 7 (after Auckland's Mitch Karpik in 2014) to lift this trophy.
There were several rugby luminaries on hand, including Sir Colin Meads, in his King Country blazer, Sir John Graham, who presented his trophy, Graham Mourie, who handed over his cup to Canterbury, and Michael Jones, who presented the trophy that carries his name to Counties Manukau.
"The quality is outstanding and the spirit with which this tournament has been played is fitting to the great Jock Hobbs," said Jones. "If this is a barometer on our game, then we are in good health."
Counties Manukau were the big movers. Dead last in 2014, they beat Tasman in the second tier Michael Jones Trophy final to finish ninth, and had some prominent performers, such as loosehead prop Jarrod Adams, No 8 Uini Fetalaiga and captain, centre Gene Teamo.
They had to work for it, though, against a committed Tasman, who led at halftime and then 28-25 at the fulltime whistle. They called a miss-two move from a scrum and fullback Liam Fitzsimons found himself in space. He finished well for a dramatic victory. Halfback Jonathan Taumateine continued his prolific points scoring with a try and slotting his last five goals.
"We knew we had the talent and work ethic, and it showed going down to the wire," said Teamo. "This is good exposure for the boys, coming from club rugby."
New Zealand Rugby sees the greater Auckland region as being of strategic importance but, aside from Counties Manukau's heroics, there must be concern that Auckland A placed just seventh and their B side came last, falling 29-17 to Heartland.
Auckland A did field Rieko Ioane, but more 1A schools stars need to be filtering into this team than was the case in Taupo over the week-long tournament.
North Harbour, the top Blues seeds, came sixth, a slight improvement on their seventh position from 2014.
NZ Rugby general manager of rugby Neil Sorensen congratulated Canterbury, Counties Manukau and Gamble, and applauded all teams for contributing to a tournament of high quality and committed rugby.
"All the teams taking part, and specifically Canterbury, should be proud of their performances over the week in Taupo. The tournament was an outstanding success on and off the field, with all teams delivering quality and competitive performances.
"The tournament provided the perfect bridge for players between secondary school and the Under 20 age group, delivering a great pathway for our young players to develop their game before moving up through the ranks.
"We expect the vast majority of players who will go on to represent New Zealand at the World Rugby Under 20 Championship next year will have played over the three days.
"It's been a great week here in Taupo and we are thankful to the Taupo Council as well as King Country Rugby for supporting another successful tournament," said Sorensen.
Jock Hobbs Memorial national U19 tournament
Day three: playoffs/finals
Premiership: Graham Mourie Cup final: Canterbury 41 (Charlie Gamble 2, Matthew Morrison, Joel Hintz, Fraser Scott tries; Brett Cameron 5 con, 2 pen) Waikato 35 (Shelford Murray, Amanaki Savieti, Sekope Moli-Lopeti, Aaron Preest, Christian Kelleher tries; Matthew Lansdown 5 con) Halftime: 21-17 Waikato
3-4: Taranaki 28 Otago 23; 5-6: Wellington 38 North Harbour 11; 7-8: Auckland A 48 Manawatu 13
Championship: Michael Jones Trophy final: Counties Manukau 32 (Tevita Setefano, Gene Teamo, Jonathan Taumateine, Liam Fitzsimons tries; Taumateine 3 con, 2 pen) Tasman 28 (Cory Whakatihi, Latu Siaki, Brendon Asomua-Goodman tries; Cory Bovey 2 con, 3 pen) Halftime: 16-15 Tasman
11-12: Southland 14 Hawke's Bay 13; 13-14: Bay of Plenty 20 Northland 7; 15-16: Heartland 29 Auckland B 17