The US line-up of Alvin Harrison, Antonio Pettigrew, Calvin Harrison and Johnson clocked 2:56.35 seconds, meaning American quartets have run the nine fastest 4x400 times in history.

"Now I am going to take time out and think about my future and if I should call it a day," said Johnson.

"This was my last major meet. I will not be running at the world championships. There is nothing to be gained."

Glorious sign-off

His glorious sign-off stood in sharp contrast to the British men's team, who failed to bring home the medal they were all hoping for.

The Brits, medallists at the past two Games but hit by injury and the absence of Mark Richardson, finished sixth in the last track event of the Olympics.

The quartet of Jared Deacon, Daniel Caines, Iwan Thomas and Jamie Baulch clocked a season's best of 3:01.22 seconds.

Thomas said: "Myself and Jamie (Baulch) are used to coming away from major championships with medals.

Pretty disappointed

"This is the first time I will not be going home with a medal, so I am pretty disappointed.

"I have run three races in 30 hours and to be honest, what I did here, I did on heart," added Thomas, who saw his preparations for the Olympics dogged by injury concerns.

"I was pleased to be here, I am just gutted I am not going home with a medal, but I will be a different athlete next year."