Somerset 289 (Overton 86, Kieswetter 65, Magoffin 6-60) and 107 for 4 beat Sussex 214 (Joyce 103) and 178 (Thomas 5-40) by six wickets

Four wickets in four balls from Alfonso Thomas powered Somerset to victory in three days over Sussex. The result leaves Somerset, who have never won the County Championship, top at the halfway point of their campaign (barring an unlikely win for Yorkshire). Some supporters are beginning to whisper that this might be their year.

The result was all but assured after Thomas, the 37-year-old South African, became the first Somerset bowler to complete the feat of four wickets in four balls in first-class cricket as he sparked a collapse that saw Sussex lose five wickets in 10 deliveries without scoring a run. He also became the first man to take four in four at Taunton.

In the sixth over of day Thomas, bowling full and gaining sharp swing, first had the left-handed nightwatchman Jimmy Anyon bowled off the inside edge after attempting a push at one that swung in lavishly from around the wicket, before Rory Hamilton-Brown was struck on the boot by a full one delivered from over the wicket next ball. Ed Joyce, the form batsman in the county game right now, completed the hat-trick when he was caught behind poking at a good one, again delivered from around the wicket, that nipped into him and demanded a stroke. It was top-quality bowling.

That ended Thomas' over but, four balls later, Chris Nash attempted to cut a wide ball from Peter Trego, maintaining the pressure as he bowled without complaint into the wind, without moving his feet and edged to first slip.

Then Thomas, starting a new over, had Matt Machan bowled off the inside edge as the batsman attempted another loose drive to one he could have left. Thomas celebrated, in his words, like "a nut case" and ran down to supporters in the Marcus Trescothick Stand. "Do you think they'll name it after me now?" he joked.

Thomas is the first man to claim four wickets in four balls in first-class cricket in English cricket since 2000, when Gary Butcher was the unlikely destroyer of Derbyshire, and the first man to achieve it in any first-class cricket since 2011, when Neil Wagner did it for Otago against Wellington.

Thomas, bowling better than ever with the passing years, eventually finished with his third five-wicket haul in three successive Championship matches at Taunton as Sussex were bowled out for 178. It left Somerset requiring only 104 for victory and, although they lost three wickets for one run after a bright start, Nick Compton thrashed three sixes off Will Beer to make sure there would be no mistake.

For the vast majority of Somerset's history, a Championship title has been a distant dream. Even now, after a decade stuffed with near misses in all competitions, players and supporters are unwilling to imagine success for fear of the pain that disappointment can bring. They have had their fill of that.

But, with a battling line-up stuffed with class and experience and a bowling line-up that has a blend of youth and experience that seems to be combining nicely, confidence is rising at the club. Somerset lack neither investment nor ambition - few clubs have a higher salary bill - and Alviro Petersen will be replaced by an overseas batsman, almost certainly a South African, while he is away on international duty. An announcement is expected shortly.

While Thomas puts his sustained performance down to a large stock of anti-inflammatory pain killers - "I'll have to stock up," he said with a smile afterwards - and an ice machine that he applies to his back, shoulders, ankles and knees every day - "Just don't tell my wife how much it cost, she'd kill me" - he considers the defining moment of his career, the time in the winter of 2007-08 when Brian Rose persuaded him to join Somerset. While Rose moved on from his position as director of cricket at the end of 2012 his influence remains on the club he served so well for so long.

And while Thomas admits he considered retiring from red-ball cricket before the season - "It was the shoulder, then it was the back, and you lie in bed at night and think 'Is this the end?'" - he has plenty to play on for now.

"This could be the year," Thomas said. "I'm starting to believe. Taunton is home now for me and my family don't want to go anywhere.

"That was the first hat-trick of my professional career and has to be right up with the highlights. But yes, the turning point of my career came when a man called Brian Rose showed belief in me. I love Somerset."

If Somerset do win the Championship - and a final game away against Yorkshire already looks tantalising - it would be a popular success for most cricket lovers simply due to the affection in which Marcus Trescothick is held. No-one symbolises the spirit of Somerset more than Trescothick.

While his powers as a batsman may be dimming and he will undergo a scan on his groin after pulling up sharply while batting in the second innings, there is a sense that, after an excellent career touched by sadness, he deserves the success that has eluded him and every Somerset cricketer before him.

And if you needed one moment to sum up Trescothick's commitment, his desire, his selflessness and his humility, it is the sight of him, over after over, perched under the helmet at short leg. "Someone has to do it," he says matter of factly. Not many 38-year-old captains would take such a view.

For Sussex this was a worrying performance. They look over-reliant upon a couple of key individuals - Joyce with the bat and Steve Magoffin with the ball - and, with England calls biting hard, appear to lack depth in their squad. Such is the absence of a quality spin bowler - though Will Beer bowled better in the second innings - that Ashar Zaidi looks set to be recalled.

To rub salt in the wound, Sussex also learned that they will be without Michael Yardy for another six to eight weeks after it emerged that he is to undergo surgery on his bicep injury. With Matt Prior and Chris Jordan also likely to be absent for long periods on England duty, it leaves Sussex scouring the loan market for possible reinforcements.