Now reaching veteran status, the phenomenal eight-year-old was sent to Berkshire with questions to answer.

Having struggled on his return to the track at Navan in April, many observers tentatively suggested his glory days were now a distant memory.

How wrong they were.

Rejuvenated under Johnny Murtagh, Ballydoyle’s ball of steel ensured a guaranteed test of stamina by galloping into the lead soon after sweeping around the final bend.

A collective gasp was emitted by the huge grandstand, with many punters fearing Yeats’ jockey had pressed the button too soon.

But Ascot regulars know better than to question the sage guidance of Murtagh, who emphatically put clear water between the great horse and his rivals within a clutch of spellbinding strides.

Patkai emerged from the floundering pack to throw down a stern examination of Yeats, who passed the test with flying colours to win by three and a half lengths as the 6-4 favourite.

Geordieland, twice a runner-up to Yeats in the Gold Cup, was disappointing in third, a further 15 lengths in arrears of the hero of the hour.

O’Brien said: “Unbelievable – that’s all I can say.

“I was so sick this morning as I really believed this couldn’t happen.

“History is very hard to change, we knew we had a wonderful horse but usually fairytales don’t come true.

“You dream and dream and dream, we were in this position and we never would be again – great things can happen.

“It’s unbelievable and I want to say a big thanks to everyone involved.

“I think today Johnny had a lot of pressure on his shoulders and the way he handled it, and the way he rode it, it was something else. I couldn’t believe it.

“This is a big credit to everyone involved (with the horse) every day.

“He’s an unbelievable horse and we knew there would never be another one of him.

“How Johnny could ride him with such pressure on him. I’ve never felt pressure for any race before.”

Amidst the exultant melee in the winner’s enclosure, it almost went unnoticed that Yeats had inflicted a monumental reverse on the bookmakers, with Paddy Power predicting losses of £1.5m (€1.75m).

Not that the Ballydoyle team gave two hoots about the layers licking their wounds, of course.

Murtagh added: “Muhammad Ali told everyone he was the greatest and he was, and Yeats has shown everyone today that he is the ultimate heavyweight champion.

“I had no doubts. After Navan I looked at Aidan and he told me ’he’ll be grand for Ascot’.

“We kept saying the ground was too soft at Navan but nobody believed us and people tried to pick holes in him.

“He loves fast ground, he loves Royal Ascot and he comes alive here.

“This is one the greatest days of my riding career and the feeling I had coming past the line for the horse alone was incredible.

“I’ve had a good week but for the horse to win four Ascot Gold Cups is fantastic and the crowd turned out in force to see him.

“It’s good for racing, and Yeats is everything that’s positive about racing.”

In winning Ascot’s oldest race for a fourth consecutive year, Yeats also arrested another significant statistic.

After all, no horse of his age bracket has won the Gold Cup in over a century.

In this kind of form, few would dare back against a famous five in 12 months’ time.