Dinas started on the front foot winning 3 early free kicks with no end product. They also won an early corner taken by Nicky Bruce which found the head of James Marr but he headed over the bar.
In the 10th minute Llanwern's Dean Clifford met a cross from the right and his shot was just wide of James Curtin's left upright.
At the other end Adam Johns put in a determined run and got a shot away which proved an easy take for Rob Bloar.
Dinas were looking sharp and determined and they got the opener in the 17th minute when, from a Bruce corner, centre-back Nathan Donnelly headed home.
The home side came more into the game winning a free kick which James Bloxham headed away and a determined run down the left wing by Llanwern's Gareth Delve ended when he over-hit his cross which went out for a goal kick.
Dinas had another chance when Donnelly headed over another Bruce corner which proved costly as on 30 minutes the home side equalised when Aaron Carew slotted home a cross from Delve.
Dinas upped their game and after a Bruce free kick forced two consecutive corners, the second of which Adam Johns got a shot on target from but a defender cleared the ball off the line.
A flowing Dinas move involving Mamadu Banguraso, Bruce, Johns who fed Ryan Garland ended as he was adjudged offside.
Johns has a really good chance to put the visitors in front again when he was played through one on one with the keeper but his lob was just wide. and just before the interval he had another shot which was blocked, the rebound falling to Keiron James but his volley was over the bar.
James Bloxham sustained a foot injury early in the second half but was ok to continue after treatment. A Bruce free kick was half cleared to Johns but his effort from a wide position on the right was over the bar.
Clifford then put in a powerful run down the left for Llanwern but his shot bounced off the top of the net.
Luck ran out for Dinas then when Bloxhan sliced a clearance straight to Clifford who fired home for 2-1 just 15 minutes into the half. Things then got worse for Dinas as, after he was chopped down, Ryan Garland retaliated and was shown a straight red card. Despite this set-back Dinas were still pressing and they brought on fresh legs, Luke Swaffield and Reuben Bryl replacing Rhys Palmer and Banguraso with 20 minutes remaining.
However a powerful long range shot by Clifford beat Curtin to make it 3-1 to the hosts realistically ended the 10 men's chances of getting something from the game and they made their final substitution with 15 minutes left, Rhys Harlin replacing Nicky Bruce. However Dinas kept pressing for the final 10 minutes and a great effort by Sam Adamson just skimmed the Llanwern cross bar from 25 yards.
Curtin had to make one great save in the dying minutes with his feet to push the ball around the upright,
Dinas squad: 1 James Curtin, 2 Sam Adamson, 3 Mamadu Banguraso, 4 James Bloxham, 5 Nathan Donnelly (1), 6 James Marr, 7 Nicky Bruce, 8 Keiron James (c), 9 Adam Johns, 10 Ryan Garland, 11 Rhys Palmer, 12 Luke Swaffield, 14 Rhys Harlin, 15 Reuben Bryl.
This Saturday, 26th March, Cwmbran Celtic are the visitors to the Murch, 2.30pm kick off.