Basketball has been played in the town of Worthing since 1984, when Worthing Bears called the Worthing Leisure Centre home. In 1999, to build on their popularity and boost commercial revenue the Bears decided to relocate to the nearby city of Brighton, where the franchise had originally started. Disappointed local Bears fans, looking for a new team to follow, quickly snapped up the franchise of struggling Stevenage and in 1999, soon after the Bears had moved out, Worthing Thunder was born. An excellent debut season, playing as the Worthing Rebels, saw them finish runners up in the National Basketball League Division 1, with a 21–3 record, compared to champions Teesside Mohawks' 22–2 record, as well as reaching the National Trophy final, losing 81–78 to Teesside at the Sheffield Arena in Sheffield. The following year, 2001, saw the Thunder finish again as runners-up in the renamed NBL Conference as well as the Playoff final, both times losing out to Plymouth Raiders. Worthing's first silverware came in 2004 in the form of the National Trophy, a competition they had finished runners up for the two years previous. The 86–72 win against the Sutton Pumas at the University of Worcester capped off a less than memorable league campaign, where the team finished 5th in the new English Basketball League Conference. The 2004–2005 season saw mild improvement on the league standings, finishing 4th with a less favourable 13–9 record, but the Southerners did reach the National Trophy final for the fourth time in five years, losing out this time to league winners Sheffield Arrows 83–76. However it was the 2005–2006 season that would see Worthing's biggest triumph to date, crowned as EBL Division 1 winners with a 23–3 record. The Championship playoffs were beyond reach though as the Thunder succumbed to second place Reading Rockets in the showpiece final at Birmingham's National Indoor Arena, losing by 4 points 103–99. The feats of 2005–2006 were surpassed in the following season when as well as defending their league title with a 21–1 record, Thunder reached both the National Cup and National Trophy finals, losing the former to Manchester Magic and the latter to Reading Rockets. Some element of revenge was gained at the end of the season however, when Worthing defeated Manchester Magic at Newcastle's Metro Radio Arena to claim their first ever play-off Championship title with a 102–94 victory. On 6 February 2008, it was officially announced that the club would be exchanging hands to a new-look board of directors in a bid to step up to the elite British Basketball League, for the 2008–2009 season. This came just months after the club declined an invitation to compete in the BBL for the 2007–2008 season, a decision which angered some fans and prompted a rival bid for the area franchise from the Brighton Cougars, which eventually failed. Thunder ended the 2007–2008 rather disappointingly compared to their usually high standards, finishing the League campaign in 3rd place behind rivals Manchester and Reading. After losing not only the National Cup Final 104–89 to Manchester, but also the National Trophy in an 84–68 demolition by Reading, the last chance of silverware was squandered as they fell at the first hurdle in the post-season Play-offs. However, after years of entertaining the idea of returning top-flight basketball to Worthing, the club felt the time was then right and the decision was made to make the move to the British Basketball League, officially being accepted in May 2008.
Step-up to BBL
Though Coach Gary Smith retained the bulk of Thunder's Division One roster, players such as Dan Wardrope and Lijah Perkins were brought in to give the team much needed top-flight experience. Thunder's campaign tipped-off ironically against an old foe in Plymouth Raiders, who also made the jump from the EBL several years earlier. The game ended in a disappointing 80–104 defeat for Worthing, and it wasn't until the third game, a road trip to Cheshire Jets, that Thunder grabbed their first win in the BBL with a 91–97 victory. Their season was a mixed one overall, and even though they managed to compete with the big-boys – including a 109–99 victory at home to Scottish Rocks and an 85–88 away win at Sheffield Sharks – Worthing finished one-place above bottom London with a 10–23 record.