Last year’s British Superbike champion began the race – rescheduled from the opening round at Brands Hatch – in 15th place on the grid but after a red flag, the race was cut to eight laps and Hill romped home in 12: 55.805.
Hill’s Swan Yamaha team-mate Nori Haga followed across the line in second place, keeping a determined Josh Brookes challenge at bay to secure a first podium finish of the season.
"I went into the race with an open mind as I knew it would be a big fight from the fifth row, even in two parts," Hill said.
"The Swan Yamaha was working really well and I know everyone talks about last year's final race of the season, but for me that is one of the best races of my entire career - from 15th to the race win.
"Everyone wanted that win hard but I suppose I just wanted it the most. I am really happy, now I need to do the same in the two races tomorrow."
Initially, with the grid placings decided according to qualifying back in Brands Hatch, Hill was well down the field but after the first lap he signalled his intentions, immediately climbing to ninth.
By the time a Jon Kirkham crass on lap nine ensured the red flag came out, Hill had moved into third and that’s where he began the shortened re-run race with Brookes out in front and Shane Byrne in second.
But Hill bided his time and then overtook leader Haga with two laps remaining to seal the victory and move onto 65 points for the season after four races.
In doing so he leapfrogged Brookes, who crossed the line 1.685 seconds behind Hill, who now has 63 points while Haga – just 0.16 ahead of the Australian – moves to eighth on 26.
Alastair Seeley, who began the original race in pole position, completed a fine day for Tyco Suzuki, following teammate Brookes home in fourth place.