Questions about the Principality of Sealand

I was flying over Britain with Google Earth when I discovered this place in the middle of the Thames Estuary:
http://en.wikipedia.org/wiki/Sealand

It's an old WWII military fort, 6 miles off the coast of Suffolk. Abandoned by the army, and at that time officially in international waters, it was claimed in 1967 by the now Prince Roy of Sealand, and declared an independent state!

Quite an interesting history it has too...
http://www.sealandgov.org/history.html

 

If we were to invade and declare sovereignty, who would stop us?

 

They seem to have a habit of firing guns at people who come too close

 

If they shot at us whilst we were in British territory, surely that would be a declaraction of war?

 

It's happened before

Since 1987 Britain has claimed territorial waters 12 miles from its coast, and in response Sealand also claimed territorial waters 12 miles from its coast, agreeing to split in the middle where they overlap

 

This reminded me of the Solent Ports, which were built during the Napoleonic wars to protect Portsmouth. Apparently, Lindy St Calire (was a notorious Miss Whiplash a few years back) now owns one, and lives there.

There are some staggering feats of engineering around...