How is “safe as houses” used?

In Howards End (1992), one line is: “But, uh, lately, it came in. Safe as houses now.”

Which movie is “safe as houses” from?

The clip at the top of this page is from Howards End (1992).

Idiom

very safe

British · Heard in 16 movies

Definitions from the Oxford Advanced Learner's Dictionary, 9th edition

But, uh, lately, it came in. Safe as houses now.

Said in 8 films · #1