Takaaki Nakagami meanwhile prevailed in a breathless final-lap dice with Thomas Luthi to claim a third consecutive second place.
Pol Espargaro, who came into the British Grand Prix 21 points behind Redding, could only finish eighth. The Briton's advantage has therefore stretched to 38 points with just six races to go.
Redding took an early stranglehold on the race, diving down the inside of Nakagami at Copse and then setting a pace that the Japanese rider and Luthi were happy to follow, with the trio breaking clear of the chasing pack.
At the halfway mark Redding was finally given a touch of breathing space as Luthi and Nakagami quarrelled for the first time, but the gap was rapidly closed and a charging Nakagami then hit the front.
With three laps to go however he ran too deep going into Village, and Redding was perfectly placed to capitalise, pulling off a pass for the lead around the outside going into the Loop.
Nakagami then fell victim to Luthi, and began to come under immense pressure from Esteve Rabat, who twice set a new lap record as he closed up to the front trio in the final two laps.
Nakagami was not done however, and on the final lap launched a new attack on Luthi - which ultimately handed Redding the breathing space he needed to seal victory.
As he cruised away, Nakagami and Luthi traded places at almost every corner over the second part of the lap, before the Japanese rider prevailed by just one tenth of a second.
Luthi was able to seal only the third podium of a season ruined before it started when he suffered multiple fractures in a massive pre-season crash.
Rabat's late charge failed to earn him more than fourth, while Dominique Aegerter beat Mika Kallio and Johann Zarco to fifth.
Espargaro meanwhile finished 13s down in eighth. The Spaniard, who fell in the morning warm-up, was never a factor and found himself flirting with the fringes of the top 10 throughout the race.