After the country’s first gold-medal win of the 2012 Olympics Tuesday, spirits in Britain were flying high. So was London Mayor Boris Johnson. The politico gamely agreed to travel down a zip line waving two tiny Union Jack flags to celebrate the occasion, only to get stuck halfway through the precarious trip. “Get me a rope, get me a ladder,” Johnson was heard shouting to the giggling crowd. “I think the brakes got stuck.” He was eventually pulled the rest of the way by a grounds crew.