RAM Racing pair Ian Loggie and Jules Gounon won the race on the road after a red flag during the pitstop cycle meant the race was restarted in the pre-pitstop order.
But they were classified fifth when British GT officials elected to add their seven-second pitstop success penalty - having finished second in race one - to their race time, a point RAM immediately protested.
Third on the road Kelvin Fletcher and Martin Plowman were credited with victory for Paddock Motorsport as a result, with ABBA Racing’s Richard and Sam Neary second and Kevin Tse/Chris Froggatt (2 Seas Motorsport) third.
After its protest was rejected by the championship stewards, RAM served notice of its intention to appeal, which was upheld in court on Tuesday and means Loggie and Gounon will be credited with victory.
Shaun Balfe and Adam Carroll are elevated from sixth to second after their 10s success penalty for winning race one was also annulled, with Fletcher and Plowman third.
Meanwhile in GT4, the decision to annul the race two success penalties means the Steller Performance Audi of Richard Williams and Sennan Fielding that finished first on the road is credited with victory after dropping to third behind Matt Topham and Darren Turner’s Newbridge Motorsport Aston Martin and the Century Motorsport BMW of Jack Brown and Will Burns.
As the Oulton Park result had remained provisional pending the appeal outcome, the championship was unable to apply in-race success penalties during the Silverstone round, instead deciding to add them onto the race time for that event once the Oulton result was finalised.
It had also decided not to award any championship points while the results remained provisional.
Only one position changes in the Silverstone result due to the retrospective application of success penalties, with Williams/Fielding dropping from second to third in GT4 behind the Ross Wylie/Matt Graham Valluga Porsche.
In the updated GT3 championship standings, Loggie/Gounon and Balfe/Carroll share the lead on 43 points respectively, while Silverstone winners Adam Balon/Sandy Mitchell (Barwell Lamborghini) move up to third on 39.5.
In GT4, Williams and Fielding lead the way on 72.5 points, with Topham and Turner second on 65.5 ahead of Wylie on 50.
A RAM team statement said: “RAM Racing welcomes the decision of the National Court to uphold our appeal over the way the success handicaps were applied during the second British GT championship race at Oulton Park on 17 April.
“The red flag and subsequent safety car restart meant a handicap that was designed with fairness in mind was applied with less than 19 minutes of the race to run.
“It was our opinion that the regulations do not have a provision for the handicap to be applied in this way, and this was the basis for our appeal.
“We understand the frustration over the length of time it has taken to settle this matter, and we do regret that the appeal also affected the running of the following Silverstone 500.
“However, we believe in fair and sporting competition and the application of the regulations under the exceptional circumstances of the Oulton race was not consistent with fair and sporting competition in our eyes.
“Therefore, we exercised our right to appeal, and we thank both race director Peter Daly and British GT for respecting our right to have our say in front of an independent panel of experts.
“We now consider this matter settled, and we look forward to the remainder of what will undoubtedly be a tight and hard-fought British GT Championship season.”
Success penalties will again be enforced from the 28-29 May Donington Park round as British GT expressed confidence that “the regulation has been tightened” following the unforeseen circumstances of Oulton Park.
