Johnson started out strong, proudly waving a Union Jack in each hand and beaming as he slid down the wire. But as he got to the middle of the wire he got stuck.
He was left dangling halfway down the 320m-long wire in Victoria Park, east London, calling out for a rope or a ladder.
"I think we need to test this on somebody going a bit faster," the mayor joked, as people on the ground scrambled to get him down.
Pictures of the mayor's mishap were soon trending on Twitter as onlookers wasted no time documenting his misfortune.
Johnson was in the park doing a demonstration to garner more support for free Games events from the locals..
Deshnee Subramany is our loudest employee. After slogging through various positions in marketing, advertising, radio – and a cow suit – Deshnee finally found her way to the M&G as a content producer in 2010, and was then forced to grow up by filling the position of day editor of the website. Sometimes she puts on her radio voice and guest-hosts the M&G Newsroom.If she was a superhero she would be called the Feeding Frenzy. Her passion is South African politics and revolutions. This comrade loves setting her world alight by discovering new ideas and people, and isn't afraid to laugh the loudest. Read more from Deshnee Subramany