The answer is: It would land in the River Thames. Details:
- London Bridge spans the River Thames in central London, so if it were to collapse, the most logical destination would be the Thames.
- The nursery rhyme "London Bridge Is Falling Down" refers to London Bridge itself over the Thames, not a different river.
- Historical notes confirm that the current London Bridge crosses the Thames and the river remains the defining waterway for that crossing.
If you’d like, I can share a brief history of London Bridge and how its role over the Thames has evolved through the centuries.
