A late-race penalty for the #33 Barwell Motorsport Lamborghini Huracan GT3 of Jon Minshaw and Phil Keen saw 2016 GT3 champions Jonny Adam and Derek Johnston in the #1 TF Sport Aston Martin Vantage claim their first win of 2017.
In GT4, the #100 Black Bull Garage 59 Ginetta G55 of Sandy Mitchell and Ciaran Haggerty sealed victory with an impressive double overtake on the penultimate lap.
A cloud-filled Snetterton hosted race two, with race one winner Keen in the Barwell Motorsport #33 Lamborghini being beaten to the first corner by Adam in the #1 TF Sport Aston Martin.
Disaster was narrowly averted when the Spirit of Race SA Ferrari 488 of Matt Griffin evaded the pit-wall barrier after contact with Seb Morris in the #31 Team Parker Racing Bentley Continental, as the pair scrapped for fourth off the line.
Seconds later, the GT3 lead changed again, with Keen muscling his way ahead of Adam into top spot. Meanwhile, James Littlejohn, who claimed third in race one, plummeted down the order in the #24 Macmillan AMR Aston Martin after suffering a spin through Bombhole corner.
In GT4, pole-sitter Joe Osborne in the #56 Tolman Motorsport McLaren 570S opened up a commanding gap at the front, streaking away from the race one winning #55 HHC Motorsport Ginetta G55 of Stuart Middleton.
The closest battle in the early stages saw Griffin duelling for sixth with the #30 AMDtuning.com Mercedes-AMG GT3 of Ryan Ratcliffe, with the Ferrari driver still recovering from his first lap near miss with the pit-wall.
In a continuation of their race one battle for top spot in GT4, David Pittard in the #51 Lanan Racing Ginetta surged past Middleton to claim second after 15 minutes of action at the Norfolk circuit.
Following his involvement in the start-line drama, a drive-through penalty for Morris saw the Rockingham race winning Bentley bumped down to 9th in the GT3 leaderboard.
Keen extended his advantage atop the GT3 standings to four seconds ahead of Adam, whilst the first retirement of race two came when the sickly #29 In2Racing McLaren 570S GT4 of Euan Mckay peeled into the pit-lane with mechanical problems.
Moments later, a spin for the #59 Black Bull Garage McLaren of Akhil Rabindra was followed up by a collision between the #43 Century Motorsport Ginetta and the #7 Team Parker Racing Bentley of Callum Macleod through Brundle corner.
The #7 Bentley was forced into an untimely pit-stop to fix damage, seeing Macleod fall to the bottom of the GT3 class before stuttering to a stop down the back-straight with further problems.
After firing ahead of Ratcliffe, Griffin in the Ferrari 488 set his sights on fourth placed Jon Barnes in the #11 TF Sport Aston Martin GT3, whilst Sam Tordoff gradually clambered up to the back of the slowing Adam in second.
Despite serving a 10-second success penalty awarded for victory in race one, the #33 Lamborghini of Minshaw maintained the lead after the second placed #1 Aston Martin was delayed in the pits by the stalled #501 PMW Expo Ginetta GT4 of Mike Robinson.
With 20 minutes remaining, the safety car was deployed to rescue Macleod’s #7 Team Parker Racing Bentley, seeing Minshaw’s advantage over Johnston’s #1 Aston Martin nullified.
A pulsating battle for the GT4 lead developed after the safety car departed, with Will Tregurtha‘s #55 HHC Motorsport Ginetta claiming the lead from Alex Reed. Tregurtha and Reed ran wide whilst battling, allowing the #100 Black Bull Garage 59 McLaren of Mitchell to sensationally swoop ahead of both and take top spot.
The GT4 lead battle took another twist, when Tregurtha hitting the #63 Autoaid/RCIB Insurance Racing Ginetta of Sam Webster at the final corner caused mayhem. The HHC Motorsport man suffered damage, before going straight on at turn one and clattering the tyre barrier, ending the championship leading Ginetta’s chances of a Snetterton double.
Controversy struck in the final 10 minutes, with the leading #33 Lamborghini Huracan of Minshaw being awarded a drive-through penalty, seeing Johnston’s #1 TF Sport Aston Martin handed race victory.
With the #6 Barwell Motorsport Lamborghini of Liam Griffin safe in second, a gaggle of cars squabbling for third in GT3 saw Rick Parfitt muscled wide by Mark Farmer, as the #11 Aston Martin held on to claim a podium double for TF Sport. In the waning moments, Jack Mitchell superbly held off a recovering Minshaw to claim fifth spot at the flag.