In the song by Fergie of the same name the music starts with fire sirens.
In her debut song, "London Bridges", Fergie makes the following context;
'How come every time you come around
My London London Bridge wanna go down'.
Abstractual concept - (Imagine how one's panties would slip of both legs evenly, they would form a bridge.)
2. Can also be a reference to implcating intercourse (depending on word usage) ie. "I want to get into her London Bridges".
"Why don't you drop the london bridges, so we can get busy?"
2.) The woman was found weeping on the side of the road. The police suspect a London Bridge.