The 35-year-old Scot, who had crashed moments after putting his Cadbury's Boost Yamaha on to pole start for the two 15-lap races at the Leicestershire circuit, was always in charge as he made a perfect start to the defence of the crown he clinched in the final race of last year.
Mackenzie made a great start in the opener but was soon overtaken by the Isle of Man TT hero, Steve Hislop, falling back to fourth place as Jim Moodie and Matt Llewellyn both nipped ahead.
"It took me a few laps to actually feel comfortable but then I put the power down and made the move," Mackenzie explained.
Once ahead on the sixth lap, there was no catching him, and behind him Red Bull Ducati team-mates John Reynolds and Hislop took the placings.
Mackenzie was sixth on the opening lap of the second race but was soon carving through the pack, putting in a decisive 93.79mph sixth lap to take the lead and power into the distance. Behind him, his new team-mate Chris Walker took second place ahead of Ducati's Sean Emmett.
"This is the dream start. There is still a long way to go but I am feeling good and there is more to come from the bike. I am feeling confident," Mackenzie said.
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