Original: Johnson was present at the closing ceremony of the 2008 Summer Olympics in Beijing as London's representative to receive the Olympic flag from Guo Jinlong, the Mayor of Beijing in order to announce formally London as Olympic host city.
Simplified: Johnson was present at the closing ceremony of the 2008 Beijing Olympics as London's representative to receive the Olympic flag from Guo Jinlong, the Mayor of Beijing in order to formally announce London as Olympic host city.