LONDON — Michael Phelps lingered on the blocks, not wanting to make another shocking blunder. The 19th medal was his. All he had to do was avoid a DQ, then set off on what amounted to four victory laps.

Down and back, then down and back again, the roars getting louder with each stroke.

When Phelps touched the wall, he finally had gold at his final Olympics.

And a record for the ages.

Phelps swam into history with a lot of help from his friends, taking down the last major record that wasn’t his alone. He took the anchor leg for the United States in a gold medal-winning performance of the 4x200-meter freestyle relay Tuesday night, earning the 19th Olympic medal of his brilliant career, and the 15th gold.

A more appropriate color.

“I’ve put my mind to doing something that nobody had ever done before,” Phelps said. “This has been an amazing ride.”

About an hour earlier, Phelps took one of his most frustrating defeats at the pool, blowing it at the finish and settling for silver in his signature event, the 200 butterfly.

That tied the record for career medals held by Soviet gymnast Larisa Latynina, but it was hardly a triumphant moment. Phelps slung away his cap in disgust and struggled to force a smile at the medal ceremony.

But any disappointment from that race was gone by the time he dived in the water on the relay, having been staked to a huge lead by teammates Ryan Lochte, Conor Dwyer and Ricky Berens.

Before the race, they all huddled together, fully aware of their role in history.

“I thanked those guys for helping me get to this moment,” Phelps said. “I told those guys I wanted a big lead. I was like, ‘You better give me a big lead going into the last lap,’ and they gave it to me. I just wanted to hold on. I thanked them for being able to allow me to have this moment.”

Berens handed off a lead of nearly 4 seconds to Phelps, who was extra cautious with the exchange, knowing the only way he could ruin this one was to get disqualified.

Lochte stood on the deck, waving his arms. Dwyer and Berens pumped their fists. And Phelps touched the wall for his first gold of the London Games with a cumulative time of 6 minutes, 59.70 seconds.

No one else was close. France’s Yannick Agnel swam a faster final leg than Phelps, but it wasn’t nearly good enough, his country taking silver in 7:02.77. China was far back in third at 7:06.30.

Phelps might have backed into the record a bit by failing to win any of his first three events at these games, but there’s no denying his legacy as one of the greatest Olympians ever — if not the greatest.

“The legacy he has left behind for swimming is fantastic,” said South African Chad le Clos, the guy who beat him in the butterfly. “Even in Africa, everyone knows Michael Phelps.”

Phelps has 15 golds in his career, six more than anyone else, to go along with two silvers and two bronzes. After failing to medal in his only race at the 2000 Sydney Games, he won six golds and two bronzes in Athens, followed by his epic eight gold medals in Beijing. And now the swan song, not nearly as epic but enough.

Latynina won nine golds, five silvers and four bronzes from 1956-64.

“You are now a complete legend!” the public-address announcer bellowed, accompanied by the Foo Fighters’ song “Best of You.”

Phelps still has three more events in London before he retires, three more chances to establish a mark that will be hard for anyone to touch.

“It has been a pretty amazing career,” the 27-year-old said, “but we still have a couple races to go.”

Several fans held up a bedsheet with “PHELPS GREATEST OLYMPIAN EVER” handwritten on it.

Hard to argue with that, though this hasn’t exactly been the farewell Phelps was hoping for — a sluggish fourth-place finish in the 400 individual medley, a runner-up showing in the 4x100 free relay, then another silver in the 200 fly.

The 200 fly was a race he had not lost at either the Olympics or world championships since Sydney, when he finished fifth as an unknown 15-year-old just soaking up the moment, a kid with big dreams but no idea they would turn out like this.

Phelps, after leading the entire race, tried to glide into the wall instead of taking one more stroke. Le Clos took that extra stroke and beat Phelps by five-hundredths of a second.

“Obviously I would have liked to have a better outcome in the 200 fly,” Phelps said. “I was on the receiving end of getting touched out. Chad swam a good race. I’ve gotten to know him a little over the last year. He’s a hard worker, he’s a tough competitor and he’s a racer.”

Le Clos pounded the water when he saw the “1” beside his name.

“He has always been an inspiration to me and a role model,” le Clos said. “I’ve watched all his races a million times and I’ve run the commentary over and over. Now, I guess I can watch my race.”

Phelps hung on the lane rope and buried his face in his hands, disgusted with himself for having squandered what looked like a sure gold. Le Clos won South Africa’s second swimming gold of the games in a time of 1:52.96. Phelps finished in 1:53.01, while Japan’s Takeshi Matsuda took the bronze in 1:53.21.

“It’s obviously my last one,” Phelps said. “I would have liked to win, but 1:53 flat isn’t a terrible time. When you look at the picture of it, it’s a decent time.”

In the first final of the night, American Allison Schmitt won the 200 freestyle with a dominating performance that left everyone else, including teammate Missy Franklin, battling for the other medals.

Schmitt won in an Olympic-record 1:53.61. France’s Camille Muffat took silver in 1:55.58.

London Olympic Medals

53 of 302 total medal events through Tuesday.

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