Trainer Aidan O'Brien and jockey Joseph O'Brien, his son, had surprisingly failed to secure a winner in the first two days of the meeting, but the duo stole the show on day three.
After getting up and running when Bracelet stayed on strongly to win the Ribblesdale, Aidan O'Brien became the most successful trainer in Gold Cup history when Leading Light held off the challenge of last year's winner Estimate.
The prolific Irish trainer has now won the prestigious race six times, while it was his son's second triumph in the Gold Cup and they will be eager to add to that double in the final two days in Berkshire.
Joseph O'Brien was given a seven-day ban for excessive use of the whip aboard Leading Light and a further two-day whip ban following his ride on Carlo Bugatti in the last race of the day, as well as a £3,000 fine, but that would not take the gloss off his exploits.
They now turn their attention to further success on Friday and will hope that Century can strike in the Queen's Vase (17:00 local time).
Leading Light won the Queen's Vase last year and Aidan O'Brien has proved that he knows what it takes to win the race by landing three of the last seven renewals.
A bold showing is also expected from the John Gosden-trained Marzocco in the hands of William Buick, who will still be on a high after winning the Prince of Wales's Stakes under The Fugue on Wednesday.
Hartnell, ridden by Joe Fanning and trained by Mark Johnston, is also expected to be in the mix.
Joseph O'Brien is aboard Tapestry in the Coronation Stakes (16:25), but My Titania, Lightning Thunder and Rizeena are among the fillies expected to make the running in the Group One.
Adelaide is a strong contender for Ballydole in the King Edward VII Stakes (15:45), with the Michael Stoute-trained Snow Sky and Western Hymn, under Richard Hughes, strong contenders.
Bold Sniper, ridden by Ryan Moore and trained by Stoute, has been well backed to land the Wolferton Handicap (15.05) and there are a further two races on the card on the penultimate day of the meeting.