Cardiff Blues overcame the spirited resistance of Scarlets' 14 men to win an eventful and refreshingly entertaining Pro14 Welsh derby.
Unlike some of the festive period's turgid earlier encounters, an incident-packed first half saw Jonathan Davies put the Scarlets in front before Cardiff Blues hit back with brilliant tries by Willis Halaholo and Rey Lee-Lo.
Scarlets' Liam Williams was then sent off shortly before the break for leading with his head into a ruck and making contact with the head of Shane Lewis-Hughes.
The visitors recovered to lead through Sione Kalamafoni's try but Cardiff Blues responded with a Tomos Williams try and two Jarrod Evans penalties to secure a memorable victory.
This was not only a notable win against Wales' strongest region in recent seasons but an admirable display of strength from Cardiff Blues just days after the departure of head coach John Mulvihill.
The game itself, a thrilling spectacle, was also a fillip for Welsh domestic rugby after it had been maligned following a series of ugly derbies, viewers turned off by a lack of attacking ambition and endless, aimless kicking.
Statistics suggested this encounter would serve up more of the same; Cardiff Blues (with 270) and Scarlets (263) had kicked from hand more often than any other Pro14 side during this campaign.
However, those of a more optimistic disposition needed only to glance at the teamsheets to find reason to hope this game might be different.
Of the 14 backs on display, 12 were full internationals and three were British and Irish Lions - though the two without senior caps played starring roles in a bright opening quarter.
Scarlets fly-half Dan Jones was one, his delightful floated pass creating space for Wales and Lions centre Davies, who crashed through for the game's first try.
Not to be outdone, Jones' opposite number Jarrod Evans flummoxed Davies with an extravagant dummied pass before setting Cardiff Blues' sole non-senior international Halaholo - albeit a Wales squad member - on his way to sprint over for a fine score.
The next was even better, Evans again the creator with another dummy and weaving run before passing to Tomos Williams, who fed Lee-Lo to finish superbly in the corner.
That put Cardiff Blues 18-10 up and Scarlets hopes of forcing themselves back into the contest were dealt a severe setback when Liam Williams was sent off three minutes before the interval.
The Lions back had been fizzing with aggression all evening, looking for confrontation wherever he could find it. He went too far, however, when he charged into a ruck with his head and made contact with the head of his Wales team-mate Lewis-Hughes.
Referee Craig Evans consulted with television match official Sean Brickell and was left with little choice but to show Williams a red card.
While Williams was left to consider how long a suspension he now faced, his team-mates were left to pick up the pieces on the night.
Leigh Halfpenny cut their deficit with a penalty early in the second half and, despite being a man down, the away side put their opponents under sustained pressure.
They eventually got their reward as Kalamafoni powered over from the base of a scrum to put the Scarlets back in front, 20-18.
But Cardiff Blues had the final say, James Botham gathering a cross-field kick and showing fancy footwork to keep alive a move which was finished with Tomos Williams darting over in the blindside corner.
Evans missed his conversion but made amends with another two penalties to seal his side's victory in a pulsating encounter.
Cardiff Blues: Matthew Morgan; Josh Adams, Rey Lee-Lo, Willis Halaholo, Hallam Amos; Jarrod Evans, Tomos Williams; Corey Domachowski, Liam Belcher, Dmitri Arhip, James Ratti, Cory Hill (capt), Shane Lewis-Hughes, James Botham, Josh Turnbull.
Replacements: Ethan Lewis, Rhys Carre, Dillon Lewis, Seb Davies, Alun Lawrence, Lloyd Williams, Ben Thomas, Aled Summerhill.
Scarlets: Leigh Halfpenny; Liam Williams, Jonathan Davies (capt), Johnny Williams, Steff Evans; Dan Jones, Gareth Davies; Phil Price, Marc Jones, Pieter Scholtz, Tevita Ratuva, Sam Lousi, Blade Thomson, Josh Macleod, Sione Kalamafoni.
Replacements: Ryan Elias, Kemsley Mathias, Javan Sebastian, Josh Helps, Ed Kennedy, Kieran Hardy, Sam Costelow, Paul Asquith.
Referee: Craig Evans (WRU)
Assistant referees: Ben Whitehouse, Mike English (both WRU)
TMO: Sean Brickell (WRU)