Securing a mast from separation and theft?

I have a 3m swaged mast, and I was thinking about it today, its just inside my boundary line, and I got to thinking, what is to stop someone just walking past and going wow I can steal that, obviously I could run a bolt through it, but I was wondering what other solutions people might have?

I thought about getting a laptop security cable and a welder, but I think that might be overkill.

I guess it depends on what you have nearby to secure it to? It’s not a problem I have to deal with though because my mast (9m-ish) is in an enclosed back garden.

Bare in mine that any holes you make in the mast will weaken it.