Ten of the 20,000 Olympic "games-makers" volunteers were also volunteers at the previous games in London in 1948.
One of them, Dr David Wright, explains what is different compared to 64 years ago.
"I have 16,000 spectators coming towards me at the entry gate," he told Evan Davis.
"[I say] welcome to the site of the Hackney dog track of years ago [where] our new brilliant stadium now is."
But given that he had done it before, he did not think he would succeed in his application to be accepted as a volunteer.
"Quarter of a million of us applied," he said.
"I did it with tongue in cheek thinking they didn't want an old fogey like me."
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