Johnny Murtagh was left counting the cost after bagging the Darley July Cup on former Australian horse Starspangledbanner at Newmarket.
The Irishman was given a six-day ban by the local stewards, ruling him out of the King George VI And Queen Elizabeth Stakes meeting at Ascot and the first two days of Glorious Goodwood, which includes the Sussex Stakes.
Having slightly missed the kick on the Golden Jubilee winner, Murtagh tacked left over to the far rail, a manoeuvre the officials deemed careless riding.
Barring a successful appeal, he will be out of action from July 23-28 inclusive.
It was King's Stand winner Equiano who was setting the blazing pace up front and the pair had it between them throughout, but with a furlong to run Starspangledbanner, the 2-1 favourite, looked beaten.
However, the Australian import showed guts to match his ability and dug very deep to land a double last achieved by Les Arcs in 2006.
The son of Choisir - who also landed the Golden Jubilee at Ascot but had to settle for second in the July Cup - won over a mile Down Under and arrived in Europe with a huge reputation.
Although initially failing to live up to the hype on his debut at York, he produced the goods at Royal Ascot having produced sensational times on the gallops at Ballydoyle - something which has continued to impress in the following weeks.
Once on the rail, Starspangledbanner was always in front rank but faced an uphill battle to shake off Equiano through the final quarter mile.
The pair exchanged blows right to the wire with Starspangledbanner just shading the advantage.
Trainer Aidan O'Brien said: "Johnny made the decision to go over to the far rail and it paid off."
"It is very unusual for a horse to have that much speed and also show that courage. He was unbelievably tenacious at the end of it."
"He is much quicker in his work than Mozart was and I could not believe he won over a mile in Australia due to the speed he shows."
"There was a lot more to lose today in comparison to Ascot and it was a big thing to come here."
"In his last piece of work he covered four furlongs in 45 seconds and he is the most incredible horse."
"All the signs were he had improved since Ascot and he showed unbelievable tenacity at the end of it."
"The plan was for him to return to Australia after Ascot in time for the covering season, but everyone agreed to bring him here."
"To have a horse like him is so special and the lads (at Coolmore) will now have to debate hard to see if he is going into quarantine and returning to Australia, or staying in training."
"I'll also put my penny's worth in and as you will all know, I would love him to race on."
"He has such quick reflexes and he is so quick out of the gate and so quick into top gear."
"It is a genetic thing and for a horse to have that speed and tenacity is unusual."
Murtagh, who described the ban as 'leaving a bad taste', said: "Not many horses win this after winning at Ascot, but he's not just got class, he's got plenty of guts and he's hardy."
"I thought the rail would help my horse, I had to make my own mind up and it helped win the race."
"Stamina helped us win it, some Australian horses don't go up the hill but this lad does."
Barry Hills said of Equiano: "He ran a marvellous race, probably a career-best and I think he was just beaten by a slightly better horse."
"He certainly gets six furlongs, but I think we'll go to York now for the Nunthorpe."
Trainer Paul Messara said of the third home Alverta: "She travelled over pretty rough before Royal Ascot and lost a lot of weight and it took a while to get her back."
"It was a great run, I'm very pleased and she'll probably have one more in the Prix Maurice de Gheest and then that will be it."
Murtagh would have been riding O'Brien's Irish Derby winner Cape Blanco in the King George in what looks set to be one of the best renewals of the race in recent years.
Derby winner Workforce and his Sir Michael Stoute-trained stablemate Harbinger are both on target for the race in which the Freemason Lodge handler saddled an impressive one-two-three last year.