Luton, who ended 2016 with a strong 81-0 victory against Rushden & Higham struggled to keep their emotions under control in an incident packed match.
The hosts opened the scoring 7-0 after 25 minutes as their forwards continued to press the Luton defence which was lacking in depth.
However, Jake Hobbs’ try five minutes later indicated a possible turnaround for the Newlands side, bringing the game to within two points as the referee blew the half time whistle.
As the second half kicked off, it looked as though it was still all to play for. However Luton made it too easy at times for Belgrave as they convert another try three minutes after the break.
A high tackle deep within the Luton half gave Belgrave a penalty which added a further three points to their tally, as the score stood at 17-5.
With five minutes of normal time left, Steve Allen scored a try after a maul carried the ball to the home side’s try line.
However, emotions spilled in extra time with multiple incidents unfolding while Belgrave still managing to score a converted try despite the chaos as the final whistle blew.
First team manager Evans believes his side’s “indiscipline” played a part in Saturday's loss,
He said: “There was some scrappy play, which I think was causing some frustration.
“What the team need to do is to is to control that frustration so that it does not spill out, not just to each other but to the referee and the opposition.”
First team coach Paul Alston rued the missed opportunity as Luton left without a point.
He said: “The forwards should have been a bit more proactive around the lineout which cost us.”