Former WBO world champion Smith had been cut under his left eye in the opening round, but after being on the back foot again in the third, the 33-year-old regained composure to find his own range.
Fowler was himself cut in the fourth and then another big hand from Smith sent him down in the next.
Although bravely trying to force his way back into the contest, another sweeping left from Smith sent Fowler down to the canvas again in the eighth round.
Although Fowler got back up to his feet, the referee waved the contest off, as Smith jumped on the ropes to celebrate a memorable victory in front of a home crowd.
Earlier on the undercard, Shannon Courtenay surrendered her WBA bantamweight title to Jamie Mitchell by majority decision – 97-93, 96-94, 95-95.
Bermondsey fighter Ted Cheeseman lost his British super-welterweight title to Troy Williamson after being stopped in the 10th round.