But they did not find it easy. Llanelli went down proudly, but ultimately Cardiff had the harder edge and held firm under intense late second-half pressure. The tie appropriately ended with Cardiff on the Scarlets line pressing for a further try. Both teams left to a standing ovation.
Defeat was easier for Llanelli to take than might have at first been thought. They had already lined up a lucrative fixture against the touring All Blacks at Stradey Park next week; but that date, 8 November, had also been earmarked for the winners of this tie to play Bath at the Recreation Ground.
Word in Wales was that they would pull out of the cup. Given Llanelli's tradition of playing touring sides, coupled with the fact that this the 25th anniversary of their historic 9-3 win over the 1973 All Blacks, it would have been entirely understandable.
There was certainly no question of them throwing the tie. They gave it their all from the kick-off, it was just that Cardiff had the classier outfit, steadier up front, sharper at the back.
But the Scarlets still displayed aggression and passion. Fists flew in a flurry of action in the opening minutes, during which the Llanelli lock Mike Voyle was shown a yellow card for getting in Cardiff faces at a penalty. Prop Hugh Williams-Jones was shown one in the second half following a clash with Nigel Walker.
Cardiff's opening try came after a period of sustained pressure followed by a break by the scrum-half Rob Howley and then a buffalo-like charge from Gregori Kacala, their Polish-born flanker. The two man overlap that the home side had developed served them well and the full-back Justin Thomas celebrated his 25th birthday with a try.
That and three Lee Jarvis penalties to one penalty by Llanelli's Craig Warlow was the sum total of scores in the opening half, but when they turned around Cardiff stepped up the pace. Howley broke, slipped a pass to his captain Jonathan Humphreys and the 18 stone Kacala, more a column than a Pole, proved unstoppable.
Jarvis converted it and it looked all over. That was when the Scarlets turned on the magic, running in three tries in less than eight minutes. The first two came from tap penalties close to the Cardiff line. Each time there was a veritable queue of red jerseys waiting for the ball.
Captain Robin McBryde crashed over for the first, then three minutes later Wayne Procter slid over. Left wing Garan Evans scored the try of the tie though. Darryl Williams burst through the thin blue line of the Cardiff defence, fed Steven Jones who then sent Evans on his way, Craig Warlow's conversion brought the Arms Park to its feet. It needed a Jarvis penalty to steady the home fans' nerves.
Cardiff: J Thomas; C Morgan, L Davies, S Hill, N Walker; L Jarvis, R Howley; S John, J Humphreys (capt), D Young, J Tait, D Jones, G Kacala, G Jones (J Ringer, 73), S Williams.
Llanelli: S Jones; W Proctor, N Boobyer, F Botica, G Evans (A Thomas, 76); C Warlow, R Moon; R Jones, R McBryde (capt), H Williams-Jones, D Hodges, M Voyle, A Gibbs, I Jones, H Jenkins.
Referee: E Morrison (England).