Michael Phelps from the United States is congratulated by Britain's...

Michael Phelps from the United States is congratulated by Britain's James Guy after winning the gold medal in the men's 4x200-meter freestyle relay during the swimming competitions at the 2016 Summer Olympics, Tuesday, Aug. 9, 2016, in Rio de Janeiro, Brazil. Credit: AP / Martin Meissner

Michael Phelps has claimed the 21st gold medal of his career, anchoring the United States to a dominating victory in the 4x200-meter freestyle relay.

About an hour after winning gold medal No. 20 in the 200 butterfly, Phelps completed his grueling double with a triumphant four laps of the pool.

The result was no longer in doubt by the time Phelps dove in. Conor Dwyer, Townley Haas and Ryan Lochte made sure of that, handing off a commanding lead to the most decorated athlete in Olympic history.

Phelps essentially spent the next 100 seconds or so on a victory lap, the crowd’s cheers growing louder with each stroke. He touched in 7 minutes, 0.66 seconds, a full body length ahead of Britain’s James Guy.

The British earned silver in 7:03.13, while Japan took the bronze in 7:03.50.

When it was done, Phelps simply sat on the starting block, thoroughly exhausted. He motioned at his neck as though he had nothing left to give.

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