Andy Hall wrote in
:

In practical terms there are three ways that I can think of that
he might be detected.

- There's a fire and he gets toasted because he can't escape

- Somebody finds out that he's running a business and reports
him the the local authority. This may be contrary to a
covenant or planning condition of when the place was built and
they decide to investigate.

- He wants to sell the house - although then he could probably
remove his little den.


Maybe having it featured on TV could also be a bit of a giveaway? :-)