They had an observation post through which they could look at the movements of vessels in the bay. Naturally, it wouldn’t be the most detailed information, but something like “a whole fleet of big German warships have entered” would be extremely valuable to know. The British navy could strike somewhere else, knowing that these ships were far away, or they could see if they can ambush them or prepare defenses in the mediterranean.
Fun fact: there was a hidden cave for people to be sealed into in the event of an invasion, to radio back reports from a viewpoint over the harbour.
How do you report on stuff while sealed in? I mean, I get a cable and antenna, but how do you actually learn things?
They had an observation post through which they could look at the movements of vessels in the bay. Naturally, it wouldn’t be the most detailed information, but something like “a whole fleet of big German warships have entered” would be extremely valuable to know. The British navy could strike somewhere else, knowing that these ships were far away, or they could see if they can ambush them or prepare defenses in the mediterranean.
Here’s a rather informative video about the cave and its purpose.