Same as the ones in the English Channel, go past them on the ferries to Europe or can sometimes see them flying low! Same place that "Fort Boyard" was filmed i think, or was that a Napoleonic one?
Torpedoes weren't that accurate to hit vertical "pipes" and to get close enough to lob a shell would have been very high risk. Don't forget this was WW2 not Star Wars technology.
The other factor to note is that 90% of successful defence is visual or perceived deterrents.
We don't do charity in Germany, we pay taxes. Charity is a failure of governments' responsibilities - Henning Wehn
IF you can get a copy from your library (whilst it's still there), try and get "Walls of War" by Keith Mallory & Arvid Ottar. Pub. Astragel Books. ISBN 0 906525 14 4. This shows the details of the Thames Forts which were built to same design as the Mersey Forts. Shows the construction, plans etc. Conditions aboard weren't a barrel of laughs.
To be hit by a WW2 torpedo, it would have to be a "lucky" shot.
More pictures of Mersey Maunsell AA forts can be found in this topic
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