The opportunist Cammish took advantage of a ferocious early battle between four-time and reigning champion Colin Turkington and Ash Sutton to wrestle the lead on the fourth lap, and stayed in front for the remainder of what turned out to be a 19-lap encounter.
As predicted – not least by Cammish himself – his front-wheel-drive Team Dynamics-run Honda lost a place at the start to the rear-driven Laser Tools Racing Infiniti of Sutton, while poleman Turkington established himself at the front in the West Surrey Racing-run BMW.
Turkington was soon under pressure, losing time at the chicane in particular, and on the fourth lap Sutton tried a brave move around the outside of Schwantz Curve.
That appeared to put Sutton in the clear as he was on the inside for the following McLeans bend, but he left a chink of light on the inside as he completed the move on Turkington, and it was filled in no time by Cammish.
Cammish clung on to the inside for Coppice, where a concertina resulted in contact from behind for Turkington from Tom Ingram, and the BMW nerfing the Infiniti of Sutton into a spin.
Turkington survived that incident in second place, while Rory Butcher inserted his Motorbase Performance Ford into third position.
The safety car appeared after 11 of the intended 16 laps, with Nicolas Hamilton’s Team Hard Volkswagen in the gravel trap at the chicane and Senna Proctor’s Excelr8 Motorsport Hyundai parked on the grass on the inside of Redgate.
There was a four-lap sprint to the finish, with Cammish holding off Turkington and Butcher to the chequered flag.
Ingram had dropped to fifth behind the second BMW of Tom Oliphant in the Coppice chaos early in the race, but his Speedworks Motorsport-run Toyota took fourth at the restart, with Oliphant’s resulting loss of momentum allowing Matt Neal’s Honda through too.
Sam Osborne put in a very solid drive to take seventh in the older-model Honda run by MB Motorsport, while Chris Smiley was just behind after bringing his Excelr8 Hyundai through from 14th on the grid on its competition debut.
Stephen Jelley was another big mover, the Team Parker Racing BMW 1-Series pilot wriggling through from a massive midfield scrum to claim ninth, while Tom Chilton completed the top 10 on his first race outing in a BTC Racing Honda.
Chilton’s teammate Jake Cook was a first-lap victim of contact with Jake Hill, but recovered to 13th ahead of the charging Sutton, who took fastest lap on the final tour.
Hill subsequently retired his MB Honda from a strong seventh place.