Plato, who started from pole position, held on to the lead from Honda Yuasa Racing’s Gordon Shedden and team mate Sam Tordoff who came home in second and third respectively.
Having had a couple of hair-raising slides, championship leader Andrew Jordan had to settle for fifth with Tom Onslow-Cole coming through to take fourth for Airwaves Racing.
A heroic drive from the back of the field by Matt Neal saw him finish in sixth in the second Honda Yuasa Civic, keeping his championship hopes alive.
A disappointing start to the weekend for eBay Motors saw Colin Turkington and Rob Collard go side by side approaching Paddock Hill bend on the first lap. Slight contact between the two resulted in Turkington spinning in his rear-wheel drive BMW and collected by team-mate Nick Foster.
Adam Morgan finished eighth ahead of the battling Airwaves Racing duo Mat Jackson and Aron Smith – who rounded out the top ten having started from the back after yesterday’s huge FP2 crash.
After spinning coming out of Paddock Hill Bend, Lea Wood handed the Jack Sear’s win to Shaun Hollamby in the AmD Tuning Volkswagen Golf, also collecting a championship point in fifteenth.
Warren Scott was also a victim of the horrendous conditions, whilst Ollie Jackson retired in the pit lane with a broken driveshaft.
The second race is due to get underway at 14:22 with the championship battle still all to play for.
Race One Classification:
1. Jason Plato
2. Gordon Shedden
3. Sam Tordoff
4. Tom Onslow-Cole
5. Andrew Jordan
6. Matt Neal
7. Rob Collard
8. Adam Morgan
9. Mat Jackson
10. Aron Smith
11. Dave Newsham
12. Jack Goff
13. Dan Welch
14. Jake Hill
15. Shaun Hollamby
Fastest lap: Jason Plato – Lap 11 – 1:43.721 By Nikki Thompson – Photos by Marc Waller