Gary Anderson held off a fightback from Rob Cross to win 4-3 and set up a quarter-final meeting with Luke Humphries.
The two-time world champion took his head-to-head record against Cross to 13-2 with a dramatic victory which saw him spurn several good opportunities to close the door, before finally doing so in the deciding set.
Anderson led 2-1 after a brilliant 170 checkout secured a break of throw in the third set, and extended his advantage with finishes of 102, 116 and 60 in the fourth set.
Cross though refused to give in, first throwing a 144 finish to win the fifth set and reduce the gap to one, and then fighting back from 2-0 down in set six to pinch it and take the match the distance.
With the darts in set seven, Cross was back as favourite until another 12-dart leg against the throw saw Anderson earn his second chance to throw for a place in the last eight, and this time he took it as his fifth match dart found the target.
"I went back to the old darts and they were working a treat," Anderson, world champion in 2015 and 2016, told Sky Sports. "I was doing all right. I was 3-1 up and made a complete mess of one leg.
"Rob stuck in and came back. But there were no nerves. I win and it’s fantastic to get through. If I get beat I go home and spend a few extra days with the family. No pressure whatsoever."
All Wright on the night
The anticipated epic in the final match of the night failed to materialise as Peter Wright beat Ryan Searle 4-1 to complete the quarter-final line-up.
Wright played well, averaging 98.91, hitting seven maximums and two 100-plus finishes, but the story here was of Searle's failure to test him in the way he had at the recent Players Championship Finals.
Indeed it took a brilliant 151 finish from Heavy Metal to win so much as a set, but that effort to reduce the deficit to 2-1 was as close as he got to troubling the 2020 world champion who remains favourite to come through the bottom half of the draw.
Wright himself needed six darts to close out the match at the end of the fifth set, prior to which he'd nailed a 132 checkout to all but confirm the outcome as Searle noticeably struggled with his action. The result though had felt inevitable for some time.
"I thought it was going to be a lot closer," said Wright. "He's an amazing player, I've talked him up in the past, he's going to be a top-five player. It just wasn't his night.
"He's an excellent player, a dangerous player; lucky enough I got away with it (because) I didn't feel comfortable at all. I struggled to find a throw. That's the way it is sometimes."
Next for Wright is Callan Rydz, who has dropped just a single set so far and will look to provide a more serious test.
"How awesome is he?" added Wright. "He doesn't care, does he? He's an amazing player. They're the guys of the future. But the old guys like me, Merv and Gary Anderson are still trying to teach them a few things."
Wade in, weighed in
James Wade coasted into the quarter-finals with a 4-0 defeat of Martijn Kleermaker, which landed a 100/30 treble for followers of Sporting Life's daily multiple.
Carl Fletcher's advice was to back Wade and Rydz to cover the -1.5 set handicap along with King to win and hit the most 180s, with only the latter causing any alarm for punters.
Playing in just his second match after receiving a bye in round two, Wade was improved here without setting the world alight, three 100-plus finishes very much in keeping with his profile.
Wade advances to the last eight without yet registering a single 180, but with freshness on his side and a 10-point uptick in his average having found the treble 20 bed with increasing frequency.
Kleermaker's highest checkout was just 58 as he struggled to see out legs against a player simply far more ruthless than he was.
Wade advances to the quarter-finals for the first time in five years and will be favourite to beat Mervyn King, which would see him match his best ever run at the one major which has so far eluded him.
AFTERNOON SESSION
Humphries wins thriller
Luke Humphries kept his cool to finally break the spirit of Chris Dobey and win a pulsating encounter 4-3.
Humphries lost the first set despite averaging 112, soon found himself 2-0 down, and then rallied from 3-1 to force a deciding set which he finally ended on double one.
It was a tenacious display from a player now in his third World Championship quarter-final, having come up against an opponent who barely missed an important dart through the opening two sets.
Dobey finally did blink in the third, missing darts for a 3-0 lead, but responded to go 3-1 up and with the throw in set five.
Humphries though broke at the start of it with a smart 90 finish, went on to win that set, and another clinical finish from 68 in set six helped him to level the match and take it all the way.
He then hit a brilliant 117 finish to break but Dobey responded with an 11-dart leg to get the match back on throw, Hollywood hitting three 180s in four visits as he again moved within a leg of victory.
Humphries then took out 56 with Dobey waiting on 12 for the match and that swung the pendulum back in his favour, a break of throw following before he appeared set to dominate what proved to be the final leg.
There was time for more drama as he missed six match darts before finally hitting double one to end a last-16 encounter which one day might be the final itself.
"Honestly, I watched Smith v Clayton last night and I thought that was the most amazing game I've seen on that stage, can anybody top it? I don't know but that was quite close!" said Humphries.
"At the end there I got human, my nerves kicked in, my hands were shaking, my heart was going mad. I think I deserved to win it in the end, but hats off to Chris, he played really well."
Humphries now heads into the last eight once more but now believes he's ready to go all the way and become a world champion.
"It's a great stat for me, three quarter-finals now out of five. I think it's time now for me to kick on. I've got more knowledge now and much more experience."
Rydz keeps rolling on
Callan Rydz lost his perfect record but enhanced his World Championship credentials with an impressive 4-1 victory over Alan Soutar.
Rydz had won all 10 sets played prior to Thursday's last-16 encounter only to see that run ended immediately, as Soutar took out 84 to become the first player to break the youngster's throw so far.
Soutar went on to win the set but Rydz began to turn the screw after they returned from a break, taking out 81 to level the match, then kicking off the third set with a 122 checkout before racing through the rest of it.
Rydz closed out set four with a 113 finish and cruised through the fifth, making it 10 successive legs to close out the match and reach his first World Championship quarter-final.
"I'm winning games, and that's the most important thing of all. Confidence is growing," confessed Rydz. "I was never going to win every game to nil, I'm happy now that I've lost a set and can concentrate on my own game. It's going well.
"If you're going to do it right, on this stage is the time to do it."
Asked whether he had a preference between Wright and Searle in the last eight, Rydz was keen to focus on the fact he's capable of beating both players regardless.
"I've played them both this year, and I've beat them both. I know I can beat them both, I've got the game for it."
On this performance, he's not wrong, though after Wright defeated Searle the level of competition and Ally Pally experience goes up considerably.
King slays Smith
Mervyn King is through to his first World Championship quarter-final since 2009 after rallying from 3-1 down to beat Raymond Smith 4-3.
King averaged just 87.29 and missed 25 darts at double, but Smith's stats were poorer still and in the end, experience made the difference.
Smith is left to rue his failure to convert a 3-1 lead but it was built on his opponent's failings as much as it was his own darts, and it took just a marginal uptick in King's performance to get the wheels of a comeback turning.
King was two legs from defeat in leg six and with the darts in Smith's favour, but the Aussie was broken in 14 darts as King went on to force a decider in which he would throw first.
The 55-year-old hit bullseye for a 124 finish at the start of the seventh set before Smith missed four darts to hold, allowing King to secure a vital break of throw.
Smith raised one more effort but by now it was too late as King found the winning double at the fifth attempt, to the delight of a crowd who had roared him on having been antagonised by Smith.
"It's unbelievable, it's unreal - it's brought tears to my eyes," said King of the Alexandra Palace support, which he hasn't always felt in his quarter-century career.
"It was building and building, through being 3-1 down, I started making my comeback and I could feel it building. Absolutely unbelievable.
"I just do what I do, growl at the board, and that's it. Raymond had a stronger feel to his game, it was nice to be able to dig in."
Asked whether he was proud to remain competitive 12 years on from his semi-final appearance, King added: "I will be when I reach the final! Who knows? At the end of the day, I've got the game if it turns up.
"It was ifs and buts today. If my proper game turns up, why not?"
Thursday's schedule & results
Thursday December 30
Afternoon Session (12.30pm GMT)
Fourth Round (Best of 7 sets)
TV Coverage: Sky Sports Darts
- Raymond Smith 3-4 Mervyn King
- Alan Soutar 1-4 Callan Rydz
- Chris Dobey 3-4 Luke Humphries
Evening Session (7pm GMT)
Fourth Round (Best of 7 sets)
TV Coverage: Sky Sports Darts
- James Wade 4-0 Martijn Kleermaker
- Gary Anderson 4-3 Rob Cross
- Peter Wright 4-1 Ryan Searle
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