Unlikely hero Paine stepped off the bench to make the decisive last-gasp score which gave Cambridge a dramatic 15-14 win over Portadown College in the Northern Bank Schools' Trophy final – their first rugby triumph since a Subsidiary Shield success in 1985.
"Mark has been in and around the team all season," Cambridge House coach Rab Gregg told Times Sport.
"He normally plays in the back row but we brought him on at half-time in the second row and he played very well and it was his hands that were on the ball right at the end.
"It was a very close game and the difference was probably that we managed to score points from nearly every chance we created, whereas Portadown missed a couple of opportunities.
"I personally feel we have maybe had stronger sides in recent years than this one, but these boys deserve their success because they have worked incredibly hard all year.
"We had some heavy defeats in the first part of the season but since the turn of the year in particular, they have worked very hard and improved a lot."
The boys' efforts were hailed at a school assembly on Friday and it is a tremendous boost for a school which traditionally hasn't been steeped in rugby success.
"There was a great turnout from the school at the final and the success will be great motivation for the boys coming up through the school.
"All being well, if everyone comes back after exams, we should only lose about five or six of this panel so hopefully we can give it a good go again next season," added Rab.
The Ballymena side trailed 11-0 at the break but Timothy Small gave them hope with a penalty early in the second half.
This gave Cambridge renewed hope and skipper Adrian Hamilton drove through from the base of a scrum for a try which small converted to make it 11-10.
Although Portadown extended their lead with a penalty, the final word went to Cambridge House in injury time when, after a driving maul from a lineout, Mark Paine was driven over the Portadown College line for a try which put the Ballymena school ahead for the first time.