Holders Newport crashed out of the Principality Cup after Cardiff and Wales scrum-half Rob Howley settled a tense quarter-final clash four minutes from time.

Howley sprinted over from 20 metres, catching the Newport defence napping, to book Cardiff's place in the last four.

"Lots of hard work, sheer guts and determination - that's what won us the game," said Cardiff coach Rudy Joubert.

"Newport were probably favourites for the competition and, now that we've beaten them, there's no reason we can't go on and win it."

But Newport, who saw their hopes of a league and cup double disappear, will kick themselves all the way home.

And although Cardiff finished the game one man short after substitute prop Ken Fourie was sent off in injury time after receiving a second yellow card, Newport had blown it in front of a capacity 13,200 Arms Park crowd.

Howley's opportunist score also got his half-back partner Iestyn Harris out of jail.

The former rugby league star was guilty of some glaring misses in front of goal, landing just four kicks from eight attempts, despite perfect playing conditions.

In the end it did not matter as tries from Howley and Wales' centre Jamie Robinson saw Cardiff home.

Harris and Howarth exchanged two penalties each during an opening 30 minutes of cat and mouse rugby.

But Howarth's third penalty during first-half injury time gave Newport a narrow but deserved interval lead.

More gaps began to appear in both defences as the second-half progressed and on 59 minutes the crucial first try was scored by Cardiff.