Penryn 25 Truro 22
Penryn fly-half Jake Seviour was the home club's hero as he landed a penalty with the last kick of the game to give his team a dramatic victory over their neighbours.
An inexperienced Truro side looked to have snatched an unlikely draw as they came back to level the scores at 22-22 after trailing 22-10.
But in a pulsating finish, Penryn won a 22m penalty after getting away with blatant forward pass and Seviour kept his nerve to pop over the kick, sparking jubilation from the home side.
It was a little tough on the visitors who had played their full part in an incident-packed Western Counties West derby and had to be content with a only losing bonus point.
Penryn had started better of the two young sides and wing Alex Ducker gave them an early lead when he brilliantly started and finished a flowing attacking move after fielding an aimless Truro clearance kick.
Seviour converted from wide out to make it 7-0 and then added a penalty to extend the home side's advantage.
Truro though were still well in the game and a brilliant run through the heart of the Penryn defence by fly half Matt Ayres saw him stopped just short of the line, but scrum-half Ricki Brandham was hand to follow up go over from close range. Justyn Irons converted from in front of the posts.
But by half time Truro were down to 13 men after yellow cards for Luke Trescothick and Tom Hinds, though they still only trailed 10-7 at the break.
After the interval though Ducker soon ran in his second try after another poor Truro kick, with Seviour converting.
An Irons penalty kept Truro in the match, but when Penryn flanker Dan Booth powered his way over for his side's third try, the game looked over, even though Seviour's conversion attempt came back off the post.
Truro though had other ideas and hit back with a try from hooker Michael Stuart, with Irons again adding the extras, after Penryn replacement Ben Keay had been sin-binned.
Then, while a mass fracas went on, wing Truro James Murdoch stole over in the corner to level the scores, though Irons' difficult conversion attempt faded just wide of the posts.
Referee Andy Reynolds spoke to both captains after the melee but issued no cards.
Perhaps a draw would have been a fair result and when Seviour missed one penalty attempt it looked as if that was the way the match would end, before his stoppage time kick gave Penryn the four points.
Penryn: Tries: Ducker (2), Booth; cons: Seviour (2), pens: Seviour (2).
Truro: Tries: Brandham, Stuart, Murdoch; cons: Irons (2), pen: Iron.
Penryn 25 Truro 22