The family run Jackson team held off the works Seats of Jason Plato and Darren Turner.
Race one winner Gordon Shedden was fourth ahead of ;pole sitter Adam Jones in a fine showing for the Team Air Cool Seat.
A chain reaction at the start of the first race eliminated several of the key players. It began with Matt Neal’s Honda touching the side of Plato’s Seat. Plato continued but Neal skidded and clipped Turkington, both cars picking up punctures.
Mike Jordan swiped Turkington’s BMW, then Fabrizio Giovanardi clipped Jordan’s car and shunted into the barrier. Jordan fell to last and the other three were eliminated – Giovanardi retiring in the pits.
The safety car was brought out but not before John George spun out at the final corner.
Jackson had made a classic BMW rear wheel drive start and shot into the lead, which he held from pole sitter Jones and the two Seats. Turner had let Plato through to third on the first lap.
Jackson kept his lead at the restart and Jones looked capable of keeping the Seats behind. But he ran wide on the exit of Cascades on lap six and Plato shot past into second.
Two other drivers were moving through the field quickly. Race one winner Shedden had moved up from his low grid position to take fifth from Tom Chilton on the fifth lap.
Jordan was also fighting back, passing Fiona Leggate and Martyn Bell on lap seven to move into ninth.
While Plato inched up on Jackson, Turner was working over Jones. Shedden and Tom Onslow-Cole caught the pair and Shedden passed Onslow-Cole on lap nine.
But when they reached the hairpin Shedden ran wide and lost the position again. Two laps later Shedden took the position for good at Knickerbrook.
Ahead Turner finally overcame Jones, diving past the older Seat at Druids. On lap 12 Shedden caught and past Jones going up Clay Hill.
Under pressure from Chilton, Onslow-Cole ran wide at Oldhall and spun away sixth place.
But there was nothing Plato could do about Jackson – who took a consummate first ever victory in the BTCC. Plato and Giovanardi are now tied for the championship lead.