By Sarah Edmonds

LONDON (Reuters) - The Olympics are defined by superlatives, the fastest, the strongest, the greatest let-down, the biggest upset, but the field vying for equestrian gold in London's Greenwich Park promises far more than its fair share.

The three equestrian disciplines of dressage, show jumping and eventing are already exceptional for their egalitarianism. The top ranks of riders include men and women, from teenagers to grandparents, all competing on an equal footing.

"We are very proud of the fact that equestrian athletes enjoy extraordinary longevity and their sporting careers span decades," Ingmar de Vos, secretary general of governing body Federation Equestre Internationale (FEI), told Reuters.

"Dressage rider Hiroshi Hoketsu, who turned 71 in March ... will be the oldest athlete to compete at this summer's Olympic Games, but he looks like a 50-year-old."

Hoketsu, whose horse Whisper adores bananas, first rode for Japan as a 23-year-old in the 1964 Tokyo Olympics.

He is not yet the oldest Olympian ever and does not expect to take that crown from Swedish shooter Oscar Swahn, who at 72 won silver in the 1920 Games, with an 2016 ride in Rio.

"Realistically, I think it's very difficult because the horse is going to be 19," he told Reuters earlier this year.

Then there is Canadian show jumper Ian Millar, who at 65 will appearing in a record 10th Games. Millar won team silver at the Beijing Games and is aiming for gold in London, but even that may not be enough to satisfy him.

"If I win a gold in London, I'd say: ‘This is good. Now I should win two,'" he said in an interview last month.

While the upper echelons are crowded with campaigners who stick around for decades, there are still plenty of young talents jostling their way to the top.

U.S. show jumping champion Reed Kessler celebrated her 18th birthday on July 9 and will become the youngest American to ride in the Olympics and the youngest ever Olympic show jumper.

Zara Phillips, Queen Elizabeth's granddaughter, and her horse High Kingdom will be a huge draw for cameras and microphones.

Phillips is the daughter of Princess Anne, who rode in the Montreal Games in 1976, and Mark Phillips, who won team eventing gold in Munich in 1972 and team silver in Seoul in 1988.

Injuries, reversals and premature retirement are par for the course in equestrian and exceptional comeback stories abound.

New Zealand's Mark Todd, a leading contender for eventing gold in London, literally wrote the book on the subject. His tome Second Chance, published this year, chronicles the double gold medalist's decision to end an eight-year retirement in 2008 and ride in the Beijing Games.

Reigning Olympic dressage champion Anky van Grunsven has more than fair chance of achieving a different superlative in London: if she reaches the podium she will have the biggest collection of Olympic hardware in the 100 years of equestrian participation in the Games.

In the course of six Olympics van Grunsven has won three individual golds, an individual silver and four team silvers.

London's equestrian venue will provide a first of yet another kind - the first international equestrian event on a raised platform, an elaborate construct to protect World Heritage Site Greenwich Park.

While there was criticism of the footing at the venue last summer, De Vos said the FEI is now happy with the surface and gave final sign-off in December.

(Reporting by Sarah Edmonds, Frank Pingue and Alastair Himmer; Writing by Sarah Edmonds; Editing by Peter Rutherford)