Birmingham 159-2 (Bell 82*, Hain 45*) beat Nottinghamshire 155 for 7 (Wessels 41) by eight wickets
Ian Bell's outstanding season continued as the Bears handsomely avenged their defeat at the hands of Nottinghamshire in last summer's T20 Blast final.
A bad night all round for the champions in front of a crowd of more than 12,000 was made worse with the news that Chris Nash, the batsman who joined them from Sussex during the off season and was expected to play a key role in their title defence, is likely to miss at least the next two matches - and possibly a few more - after suffering a shoulder injury in the field.
Nash, fielding at extra cover to Ish Sodhi, attempted to catch a solid drive from Adam Hose but landed heavily on his right side. In obvious pain, he was attended on the field by the Nottinghamshire physio before leaving the field with his shirt folded into a makeshift sling.
Peter Moores, Nottinghamshire's head coach, was not optimistic about a quick return. "I don't think it is dislocated but it could be his collarbone," he said. "He's going to hospital for an X-ray and we'll know more after that but it doesn't look great. He is going to be out for a bit, that's for sure."
Bell, who suffered the indignity of being left out of the Bears team on finals day as his form dipped across all formats and Dom Sibley was preferred, could not have delivered a more impressive retort on his return to the side, finishing unbeaten on 82 - his highest score in T20 for more than three years.
This time, the decision was to pick him rather than Sibley and he responded with an innings that was typically Ian Bell, elegantly unfussy and for the most part made up of authentic cricket shots.
Sam Hain, a young batsman beginning to ally consistency with his undoubted quality now, supported Bell in an unbroken partnership of 121 that saw his side overhaul a modest Nottinghamshire total with 16 balls to spare.
Modest indeed compared with last season's average of 196 on this ground. Trent Bridge's reputation as the place for batsmen to prosper has only been reinforced this season but after being asked to bat first on a used pitch, a Nottinghamshire side at full strength with the exception of Alex Hales could never build any momentum.
Backed up by some sharp fielding, all of the Bears' six bowlers employed good variety and all contributed, none more impressively than the 18-year-old fast bowler Henry Brookes, who is already looking a good prospect to be young player of the season.
Brookes is excelling across all formats, with 21 wickets in the Championship and nine in the Royal London Cup. This was his senior debut in this format, yet his captain trusted him to bowl at the top of the innings and at the death and he did so without a flicker of anxiety.
He could barely have started his T20 career any better, in fact, opening with a wicket maiden. Tom Moores, another young man rapidly making a name for himself, pulled him for a lusty six in his second over and Riki Wessels, always dangerous, took him for three boundaries in his third. Yet he came back for the penultimate over of the innings, with Nottinghamshire desperately looking to swell a paltry total, and conceded only three off the bat.
The Bears were on top from the start, restricting the home side to only 40 runs in the Powerplay overs. Jeetan Patel put down a chance off his own bowling when Wessels was on 30 but that was a rare error in the field and it was not an expensive one. Wessels hauled Will Rhodes over the mid-wicket boundary in the next over but then smacked a short, wide ball straight to Bell at backward point.
Wessels made 41. Apart from Billy Root's industrious 33 and Luke Fletcher's cameo assault on Patel, which yielded 6-4-6-6-1, there was not much else. Colin de Grandhomme, who mixed up his pace superbly, snuffed out two of the bigger threats in Samit Patel and Steven Mullaney.
This was a strong performance by the Bears, whose run to the final last year probably exceeded expectations. It was a substantially rebuilt side yet director of cricket Ashley Giles managed to find a winning blend immediately. He will believe they can qualify for finals day again at the very least.
With 14 matches to negotiate, there is much that can go wrong as well as right until that point is reached. There is a lot to be said, though, for putting down a marker right at the start and they did so impressively.