Because the original bridge was the ONLY bridge in London at that time.
London Bridge crosses the River Thames in London. Many years ago, when it was the ONLY bridge in London, the obvious name was London bridge.
London Bridge. The Olympic rings are on Tower Bridge - not London Bridge.
London Bridge spans the River Thames
London Bridge
London Bridge
London Bridge
Tower Bridge and London Bridge.
It is called Tower Bridge. Or you might be talking about the one that was on Harry Potter and the Half-Blood Prince, which is the wobbly bridge, but it's proper name is the Millenium Bridge.
ACOL
Tower Bridge is east of London Bridge.
The London bridge
What does London bridge represent
London Bridge.