Despite dominating the second half with possession and territory Ponty had to wait until the Pirates No 8 and try-scorer Aaron Carpenter was in the sin bin before clawing their way back in a titanic struggle.
Ponty had already butchered a clear cut scoring chance when losing the ball over the line but with the Pirates a man down, the Welsh club piled on the pressure and eventually saw hard working hooker Liam Belcher power his way over. With Humberstone adding the conversion Ponty had reduced the deficit to just one point with nine minutes remaining.
Defiantly the home side held a rampant Ponty at bay until the Pirates infringed in front of their posts and Humberstone stepped up to drill the penalty over to put his side in front for the first time in the match just 90 seconds from full time.
The match was played at a fast paced tempo throughout where a try from Carpenter and three successful penalties from the boot of fly-half Kieran Hallett looked like being enough to see the Pirates home at the break.
However Humberstone had kept Ponty in touch with two first half penalties and he had the final say with his trusty boot when condemning the Pirates to a late defeat and sending his side through to the semi-finals of the British and Irish Cup where they will face Leinster 'A' at Sardis Road.