Henderson plunders double to help Ulster secure perfect ten out of ten
Ulster 30 Scarlets 15
Ulster move into the New Year with new hope in Europe; not always a recent reality for them and often a false dawn but perhaps this time they may have renewed hope.
A ten-point haul from this December double will give them confidence they can rattle Racing here next month.
Iain Henderson's double, added to tries from John Cooney and - who else? - Jacob Stockdale, garnered the five points in an effort that was not always assured but ultimately convincing, overcoming early stutters.
On a miserable night, with a cutting wind scything towards the Memorial end with ever more accumulating rain, tactics seemed more reasonably tailored towards the boot rather than the hand.
And so, backed by the elements, Billy Burns probed territory left and right, and skywards, ensuring his side almost immediately gained the upper hand in terms of territory.
Stockdale boasted a resounding early sortie to warm those freezing in the bleachers before Cooney knocked over an eighth-minute penalty to backbone their dominance, after Ken Burns was done for an illegal poach on his opposite number and fellow captain, Rory Best.
Ulster twice crossed the line but illegally so; they were playing all the rugby, albeit inexpertly at times.
Still they returned for more and so incipiently did Scarlets' indiscretion rate as Ulster reverted to a tighter game once establishing residence in the red zone.
By the half-hour mark, referee Luke Pearce's patience snapped and he binned Wyn Jones for flopping off his feet close to the line and failing to find them quickly enough; in his absence Ulster finally pounced.
To be fair, it took them a bit of huffing and puffing before Henderson was corralled over the line by a bevy of beefy comrades; Cooney's conversion made it 10-0 and with their opponents a man down, the time seemed ripe for Ulster to put their boots on Welsh throats.
Instead, they released them, suddenly ceding possession and territory as the lively visitors wallowed in their offloading game with sufficient glee to all but eat up the yellow card period.
Indeed, by the time Jones trudged back on, Patchell had just despatched a penalty for 10-3. Scarlets' decision to opt for three might have hinted at optimism as they turned around with the favouring elements.
Ulster's anxiety was hardly released after the half-time cuppa. Burns booted out on the full and it was noticeable that, although they dominated ball again, they were struggling to pierce the speedy Scarlets defence.
One sequence of multiple phases saw Ulster slowly back-pedalling some ten yards from the initial gain-line, a marked absence of truly punishing physicality or inventive subtlety.
A second try could have provided some relief but bizarrely they found themselves level in the 49th minute when Scarlets scored with a classic counter-punch, aptly stinging a side who were struggling to land one of their own.
Cooney, digging for ponderously slow ball, flung a pass about 20 yards out but it was intercepted by his ever-alert counterpart Gareth Davies.
Off the Welshman scampered, with Addison corner-flagging him for a good 40 metres before Davies decided to kick in-field, quite expertly too, the ball rolling almost gratefully towards the line, as if awaiting collection.
Steff Evans tried to do so but Speight's attention forced him and the errant pill to collide with the post, before Jon Davies arrived to pounce as only a man nicknamed 'Fox' should.
After interminable queries via the TMO, the try stood and the Ulstermen stood motionless and stunned beneath the posts.
They needed a response and, as if their previous efforts were a mere whimsy, they produced it and from a now familiar source. Stockdale, the Six Nations record try scorer in Ireland's Grand Slam year, had scored in every round of Europe so far and he wasn't in a mind to interrupt the sequence.
Better patience on the ball created the platform for Burns to deliver another cross-field kick and, despite facing two opponents, Stockdale's progress was almost unhindered as he galloped impressively home from 20 metres out.
Cooney's conversion, and a 58th-minute penalty, pushed the game into two-score territory for the first time all evening.
Suddenly, everyone in the old ground had warmed up. With Scarlets' resistance diminishing, they now suddenly began to soak in the tackle.
In the 63rd minute, Henderson punched Scarlets in the belly by plunging over from no distance - notably another Burns cross-kick to Louis Ludik had farmed the required ground - to nab his second, and his side's third try.
A ten-point haul from this December double was now non-negotiable; Cooney ensured it arrived just three minutes later to ease his side into the home straight.
Having emptied the tank, Ulster then emptied the bench, Tom Prydie nabbing mere consolation.
Ulster - L Ludik; H Speight, W Addison, S McCloskey, J Stockdale (D Cave 58); B Burns (J McPhilips 67), J Cooney; E O'Sullivan (K McCall 65), R Best (capt, R Herring 67) , M Moore (T O'Toole 67), I Henderson, K Treadwell (M Rea 77), S Reidy, J Murphy, M Coetzee (N Timoney 67).
Scarlets - J McNicholl (D Jones 53); T Prydie, J Davies (P Asquith 60), H Parkes, S Evans; R Patchell, G Davies (S Hidalgo-Clyne 66); W Jones (P Price 67), K Owens capt (R Elias 53), S Lee (W Kruger 60), J Ball, D Bulbring, L Rawlins (P Price 29-39), W Boyde, U Cassiem.
Ref - L Pearce (RFU)