Fly-half Lee Jarvis scored 17 points as Neath strode into the Celtic League final with a convincing win over Cardiff at the Gnoll.
Neath led 17-0 after dominating the first half, before holding off a spirited Cardiff fightback and extending their lead through a clever Jarvis try and his typically excellent goal-kicking. The Neath forwards - particularly frontrowers Duncan Jones and Barry Williams - ran themselves to a standstill in a superb display of support play.
The victory earns Neath a trip to Cardiff's Millennium Stadium to play European heavyweights Munster in the Celtic League final on February 1. Munster hammered fellow Irish province Ulster 42-10 at Thomond Park on Friday night but will be wary of Neath - whose win in September 2001 is the last time a Welsh side beat them.
Neath went into the match without influential backrower Brett Sinkinson, who is out with a knee injury, but his replacement Steve Tandy continued his great form of late with two bursts up the middle of the paddock in the opening minutes to put the home side hot on attack.
Two questionable penalties from the whistle of Irishman Alan Lewis halted both moves, but Tandy's fellow backrower Alfie Mocelutu produced a great charge before butchering a simple try by trying to run over dimunitive Cardiff fullback Rhys Williams rather than passing to a clear Gareth Llewellyn. All was not lost for Neath, with Jarvis converting a simple penalty goal after Cardiff were deemed offside from the ensuing ruck.
With just 17 minutes played, Cardiff coach Dai Young was forced to take the field when prop Ken Fourie limped off, continuing the club's incredible run of injuries to frontrowers.
Impressive Neath loosehead prop Duncan Jones set up a second penalty-goal attempt for Jarvis with a bullocking run towards the line, but the ball hit the righthand upright. Cardiff backrower Emyr Lewis knocked on and Neath should have scored from the 5m scrum, but Mocelutu - not for the first time this season - spilled the ball with the line begging to be crossed.
But Cardiff couldn't defend forever, and Neath No 8 Nathan Bonner-Evans scored after peeling off the back of a 5m scrum. Jarvis' conversion took the scoreline to 10-0 on the half-hour mark.
Neath were back on attack within five minutes and another 5m scrum proved lucrative. Bonner-Evans went close before a clever Jarvis pass put inside centre Dave Tiueti over near the posts. Jarvis' conversion gave the All Blacks a well-deserved 17-0 lead after one of the most one-sided halves of rugby seen in Wales this season.
Cardiff hit straight back when scrum-half Richard Smith toed ahead down the blindside to catch the Neath defence napping, and Iestyn Harris' superb touchline conversion narrowed the deficit to 10 points.
Referee Lewis missed a Cardiff knock-on from a Harris up-and-under and rubbed salt into the Gnoll crowd's wounds by awarding a penalty to Cardiff in the same move, which Harris converted.
Just as the Neath fans' nerves were stretching, a piece of magic from Jarvis allowed them to settle back in their seats.
Some good buildup work from Neath fullback Adrian Durston and winger Shane Williams gave the home side a maul on the Cardiff tryline. The ball was spun back to Jarvis, who faked a dropped-goal attempt before cutting back on the angle to score near the posts. His conversion gave Neath a 14-point lead and Cardiff were 100/1 to breach the gap.
Jarvis kicked his 17th point after an hour and winger Gareth Morris sealed matters with a try in the corner after a clever skip pass from scrum-half Andy Moore.
Neath: Tries - N Bonner-Evans, D Tiueti, L Jarvis, G Morris; Pens - L Jarvis 2; Cons - L Jarvis 3.
Cardiff: Tries - R Smith; Pens - I Harris; Cons - I Harris. Halftime: Neath 17-0.
Neath: A Durston; G Morris, J Storey, D Tiueti, S Williams; L Jarvis, A Moore; D Jones, B Williams, A Millward, A Newman, G Llewellyn (capt), S Tandy, A Mocelutu (R Phillips 54), N Bonner-Evans (S Martin 76).
Cardiff: R Williams; N Walne, J Robinson, M Allen, C Morgan; I Harris, R Smith; T Payne, G Woods, K Fourie (D Young 17), H Senekal, J Tait (A Jones 65), D Baugh, M Williams (capt), E Lewis.
Referee: Alan Lewis (Ireland).