The length of Leading Light's neck was all that separated him from the 2013 champion Estimate, pwned by Queen Elizabeth II, at the end of a pulsating Ascot Gold Cup at Royal Ascot on Thursday.
In a pulsating finish that threatened to lift the roof clean off the £200 million grandstand, Leading Light narrowly resisted Estimate's bid to win Royal Ascot's feature race for the second year running.
For the winning trainer, 44-year-old Irishman Aidan O'Brien it was a record sixth victory in Europe's premier staying race, and was yet another landmark in his remarkable career having become the first trainer in history to win three successive Epsom Derby's earlier this month.
Leading Light's victory brought to the quietly-spoken unassuming trainer a mixture of joy and relief.
Some of his horses have run disappointingly this week, causing him to approach the Gold Cup with trepidation.
But Leading Light cast aside the doubts to become only the third St Leger winner to win the Gold Cup in the last 100 years.
"It was a tough battle," O'Brien reflected.
"It was nip and tuck all the way. That final furlong seemed to take forever.
"Obviously we are sorry the Queen's filly finished second but we are delighted to have won. It was a tight finish and we're lucky that our horse managed to get his head in front."
It was a race of high drama in which the winning post could not come soon enough for O'Brien's son, Joseph, who rode Leading Light .
His tired mount veered from side to side as O'Brien drove him forward with his whip. So much so that the jockey had to put his whip down for fear of colliding with other horses, and this allowed Estimate to mount a late rally in the final 100 metres.
But Ryan Moore, aboard Estimate, was unable to ride to maximum effect. Pinned in between Leading Light on his outer and Missunited inside him, Moore had precious little room in which to manoeuvre as he narrowly claimed second place from Missunited.
Nevertheless, Estimate covered herself in glory - not least because she suffered an interrupted preparation in the build-up to the race. She was unable to run before the Gold Cup and had to overcome an eight-month absence from the racecourse.
In the preceding race O'Brien saddled his first winner of the royal meeting when Bracelet proved too strong for 11 opponents in the Ribblesdale Stakes.
Bracelet's triumph served to steady O'Brien's nerves after the perennial champion of Ireland had drawn a blank on the first two days.
In the opening race O'Brien saddled The Great War, who was an odd-on favourite for the Norfolk Stakes. But the horse could finish only fifth of nine runners behind Baitha Alga, the mount of Frankie Dettori.
It was Dettori's second winner of the week and a third for Sheikh Joaan Al Thani, whose brother, the Emir of Qatar, arrived at Royal Ascot in the royal horse-drawn procession on Wednesday.