Hidden by the most classic of spy-movie-tricks, the hidden-door-in-a-bookshelf.
At in London, almost every room has a hidden surprise. Here, a surprise door in the floor leads to a slide into a lower-level playroom.
A little climb makes curling up with a book even more appealing.
See more amazing hidden rooms on !
And tell us in the comments: What would you keep in your secret room?