The Crown Estate
It is owned by the British Government and operated on their behalf by the Environment Agency.
The tunnel is 50.5 km long (31.4 miles). of which 37.9 km. (23.5 miles) is below the seabed.
There are many tunnels under the Thames - including several used for trains.
The only railway under the river Thames is parts of the London Underground (tube).
The river "Thames".
shelly seabed
Yes
It keeps London from being under water.
The Thames Barrier is used to prevent London from flooding. Under normal conditions it lies on the bed of the river Thames and is only raised when an exceptionally high tide is expected.
The Thames Basin is an area surrounding the River Thames, any rain falling in the Basin ends up in the Thames. It covers and area of just under 5000 square miles and some 13 million people live in the area
It is unpredictable, however statistics show that a tsunami as result is incredibly unlikely.