Centuries for Ryan Hunter and Phillipe Le Roux were the highlights of the youth interprovincials between the NCU and Leinster in the Under 15 and 17 games.
CSNI's Hunter made it two consecutive hundreds as he hit 11 boundaries in his 102 from 103 balls in the Under 15 match at Derriaghy.
He shared an opening stand of 128 with Adam Leckey who made 49 before the young Dubliners fought back strongly.
Four wickets for Olly Riley, plus two apiece for Reuben Wilson and Arshad Safi saw the hosts lose their last six wickets for just two runs to finish 213 all out.
Aaron Doyle's hard hit 57, which included six fours and two sixes kept Leinster in contention in a thrilling chase which went right down to the wire.
Adam Leckey and Harry Dyer picked up two wickets each, while there were 20s for Srihan Karpe and Olly Riley.
In a tense last over, all three results were possible going down to the last ball, but it was the NCU who held their nerve, prevailing by one run in a game that showcased all that was good about youth cricket in Ireland.
At Wallace Park two early wickets for Adam Kennedy (2-45) had the NCU on top against the LCU in the Under 17 game.
However, Railway Union's Phillipe Le Roux and YMCA's James Forbes soon changed the complexion of the contest with a brilliant third wicket partnership of 184 in 27 overs.
Le Roux top scored with 125 from 110 balls, which included 9 fours and 6 sixes, while Forbes' 81 from 101 balls had 6 boundaries as well as clearing the ropes four times.
Luke Whelan (22*) added late runs, while Max Shannon (2-52) picked up two late wickets as Leinster ended on 274 for 5.
An opening stand of 73 in 15 overs between Matthew Halliday (39) and Adam Ly (22) gave the hosts cause for optimism, but once Yash Bala broke the partnership on his way to taking 4 for 30, the innings faded away.
Matthew Cherry made 25, while James Forbes and Ahmed Shah took two wickets apiece as the NCU were dismissed for 152.
The teams are back in action on Friday with Leinster playing the North West at St Johnston and Ardmore, while the NCU face Munster at Phoenix and Civil Service.
At Queensway, Derriaghy. NCU beat LCU by 1 run
NCU 213 all out, (36.5 overs; Ryan Hunter 102, Adam Leckey 49; Olly Riley 4-28, Reuben Wilson 2-27, Arshad Safi 2-44)
Leinster 212-9 (40 overs; Aaron Doyle 54, Olly Riley 24, Srihan Karpe 23; A Leckey 2-31, H Dyer 2-41)
At Wallace Park, Lisburn, Leinster beat NCU by 122 runs
Leinster 274-5, 40 overs (Phillipe Le Roux 125, James Forbes 81, Luke Whelan 22; Adam Kennedy 2-45, Max Shannon 2-52)
NCU 152 all out (37.3 overs; Matthew Halliday 39, Matthew Cherry 25, Adam Ly 22; Yash Bala 4-30, Ahmed Shah 2-17, James Forbes 2-30)