Ingram had the medium tyre fitted on his Excelr8 Motorsport Hyundai i30 N, and started from seventh on the grid.
He made short work of the five hard-shod cars in front of him to move up to second on lap two, and set off after the leading Motorbase Performance Ford Focus ST of Dan Rowbottom.
Rowbottom was also on mediums, and passed polesitter Stephen Jelley’s West Surrey Racing BMW 330e M Sport on the second lap at Williams, with Ingram following him past on the back straight.
Ingram was soon on the back of Rowbottom, and on the fifth lap the leading Ford defended into Riches, only to run wide and allow Ingram to slip through into the lead.
Rory Butcher, who was the leading starter on soft tyres from eighth on the grid, also got past Rowbottom into the Esses.
The Scot’s Speedworks Motorsport Toyota Corolla was now 1.306 seconds behind Ingram, and despite the apparent tyre advantage he could not erode the deficit.
Instead, Cammish became a looming threat in his Motorbase Ford.
Cammish got up to third on lap seven of 11 when Rowbottom ran wide at Oggies, and on the ninth lap he got past Butcher into second place at Riches.
With two laps remaining, Cammish, who had set fastest lap in his climb from 11th on the grid, was 1.558s adrift of Ingram.
The gap was down to 0.910s with a lap to go, and by halfway round the final lap Cammish was right with the leading Hyundai.
Ingram, who has been struggling all weekend with illness, hung on for victory by 0.587s from Cammish.
But Cammish’s Ford failed the ride height test after the race for reasons which at present the Motorbase team is unable to explain, elevating Butcher to second and Rowbottom to third.
New championship leader Ash Sutton had another remarkable race to take fourth place in the final results with the unfancied hard tyre on his Motorbase Ford.
Josh Cook started from the rear with softs on his BTC Racing Honda Civic Type R, but sliced through the field and passed the warring WSR BMWs – all struggling on hards – in the late stages to take what became fifth place.
Jelley hung on as the best of the WSR BMWs to claim sixth spot, while a penultimate-lap clash at the Wilson hairpin between the sister machines of Jake Hill and Adam Morgan promoted the squad’s Colin Turkington to seventh.
Aiden Moffat also slipped past to take eighth in his BTC Honda ahead of Morgan and Hill.
BTCC Snetterton - Race 3 results (11 laps)
| Cla | Driver | Car / Engine | Gap |
| 1 | Tom Ingram | Hyundai | |
| 2 | Dan Cammish | Ford | 0.587* |
| 3 | Rory Butcher | Toyota | 5.594 |
| 4 | Dan Rowbottom | Ford | 6.869 |
| 5 | Ash Sutton | Ford | 9.428 |
| 6 | Josh Cook | Honda | 15.122 |
| 7 | Stephen Jelley | BMW | 16.241 |
| 8 | Colin Turkington | BMW | 16.349 |
| 9 | Aiden Moffat | Honda | 16.993 |
| 10 | Adam Morgan | BMW | 17.832 |
| 11 | Jake Hill | BMW | 18.096 |
| 12 | Tom Chilton | Hyundai | 18.976 |
| 13 | Bobby Thompson | Cupra/TOCA | 19.364 |
| 14 | Dexter Patterson | Cupra/TOCA | 19.665 |
| 15 | Ricky Collard | Toyota | 26.688 |
| 16 | Mikey Doble | Vauxhall/TOCA | 29.578 |
| 17 | Jack Butel | Cupra/TOCA | 30.287 |
| 18 | Dan Lloyd | Cupra/TOCA | 30.601 |
| 19 | Andrew Watson | Vauxhall/TOCA | 32.242 |
| 20 | Will Powell | Honda | 33.785 |
| 21 | Sam Osborne | Ford | 44.431 |
| 22 | Nick Halstead | Hyundai | 1'05.177 |
| (21) | Nicolas Hamilton | Cupra/TOCA | Retirement |
| (18) | Ronan Pearson | Hyundai | Retirement |
| (12) | Árón T.-Smith | Vauxhall/TOCA | Retirement |
| George Gamble | Toyota | Retirement | |
*Disqualified after car failed post-race ride height checks
