Roland Perry wrote:

In message , Clive D. W. Feather
writes
The bridge authorities used to keep lookouts for miles down the river
in case something approaching was likely to want the bridge opened.

Nowadays, as well as giving advance notice for Tower Bridge, there are
various points on the river where ships are required to radio in.

The problem is quite clear - the bridge is now operated by an Oyster reader.

--
Ian Tindale