Michael Phelps wins 17th Olympic gold medal in 100m butterfly final

The greatest Olympian in the history of the modern Games, Michael Phelps, swam his last ever individual race on Friday night and claimed his 21st medal and 17th gold with victory in the 100m butterfly.

In front of a packed and deafening crowd, expectant for Rebecca Adlington's appearance in the 800m freestyle, the race immediately following his own, Phelps started poorly and lagged dangerously in the first half of the race but swam a remarkable final 50m to come from seventh position at the turn to win the race in 51.21sec.

As befits almost the final encounter of an extraordinary career, it was an extraordinary finish, concluding with a dead heat for silver between South Africa's Chad le Clos and the Russian Evgeny Korotyshkin, both of whom touched the wall in precisely 51.44, as well as a dead heat for fourth between the German swimmer Steffan Deibler and Milorad Cavic of Serbia – whom Phelps had narrowly beaten in the same event in Beijing – each in 51.81.

Phelps has said he will not race again after these Games, meaning that his performance on Saturday evening in the final of the 4x100m medley relay will be his last competitive appearance in a swimming pool.

"I didn't have a good finish and didn't have a good turn but I am just happy to defend that title," he said immediately after emerging from the pool. "It's a good way to finish my last individual swim ever."

The win brings Phelps's medal tally from the Games to three golds and two silvers from six races, having earlier won the 200m individual medley and 4x200m freestyle relay. The swimmer, who claimed a record eight golds in Beijing four years ago, entered seven events in London but failed to win a medal in his first race, the 400m individual medley.

Earlier the Aquatics Centre had witnessed the American teenager Missy Franklin win her third gold of the Games in the 200m backstroke in a world record of 2.04.06. Britain's Lizzy Simmonds just missed out on the medals, finishing fourth in 2.07.26, behind Anastasia Zueva of Russia, who took silver, and Elizabeth Beisel of the USA.

For the 17-year-old Franklin, who has claimed 100m backstroke and 4x200m freestyle golds as well as a bronze in the 4x100m freestyle relay, descriptions as the female Phelps, inheriting the mantle of her compatriot, seem increasingly inevitable.

By Phelps's s own stratospheric standards his Olympics had begun with a disappointment and continued, for a time, to be merely excellent. After the shock of the 400m individual medley on the first day of the Games, in which his overhyped "duel" with his compatriot Ryan Lochte finished with Phelps outside the medals for the first time in an Olympic event since 2000, he could manage only a silver the following evening, when a storming French foursome stole the 4x100m relay from the USA squad in the final inches of the race.

The following day, in what was supposed to be his very best event, the 200m butterfly, he was pipped to the line by Le Clos, having to console himself with another silver. That he had just equalled the record for the greatest number of Olympic medals in history, at 19, was almost incidental.

He would surpass Larisa Latynina, the Soviet gymnast who had previously held the record, only an hour later, and his 20th Olympic medal, this time, was also his 15th gold. Another gold followed on Thursday, when he pipped Lochte on the line to win the 200m individual medley. It was as if the great swimmer had realised, at last, quite how limited were his remaining opportunities to show what he could do.

In an Aquatics Centre that has roared itself hoarse all week at the appearance of any Briton, Phelps's reception in every swim has been scarcely less rapturous. Friday night was no exception, with a mighty cheer when it became apparent he had clinched the race.

It brought a popular silver for Le Clos who, as well as claiming his first Olympic win in the 200m butterfly, had endeared himself to the world by sobbing from the podium throughout the South African national anthem, even as his father, Bert, won over millions of BBC viewers in an infectiously effusive interview after his son's win.

Le Clos has been outspoken in his admiration for Phelps, describing him as "an inspiration and role model".

In a joint press conference after the race he said the thing that had inspired him in 2009 to reach his first senior team for South Africa was the opportunity to swim against Phelps.

"It's crazy to think that he's retiring because I've always looked up to him. It's going to be hard to go to a meet now and think that he's not there.

Phelps, in response, has tipped the 20-year-old South African as having the talent to assume his dominant role in men's swimming.

Asked what would be the best aspect about no longer competing, the swimmer, who eats up to 12,000 calories a day while racing, said: "I think the biggest thing I'm looking forward to is not eating pizza and pasta every lunch and dinner. I've had the same kind of lunch and dinner every day, oatmeal and fruit and cup of coffee every morning. I'm looking forward to eating what I want when I want it."

As for how he would like to be remembered: "I always said I wanted to change the sport and take it to a new level. That's been a goal since I was 15. If I can say I have done that, that is all I want."