Terschelling

It was called the Brandaris Letter.

It was named after the Brandaris, which is a very famous historic lighthouse on the Dutch island of Terschelling.

Ah, okay, so it's a metaphor, a beacon of warning shining in the darkness.

Exactly.

Yep.

He's been on vacation to Terschelling, which is one of the northern islands in the Netherlands.

And on that island is the German bunker complex, Tegerstelling, which was the primary, I think the primary radar station used for early interdiction of bombers coming out of England.

Mm-hmm.