They are bringing the curtain down....
...On the Theatre Museum which is closing forever on 7th January, and a small bit of eccentric, less than perfectly glossy, London will be lost forever. It's never been crowded when I've been in but they do have some fascinating stuff. It will probably be replaced with some slick tourist experience or a restaurant.
If you can, pop in and see it before its too late. And yes, it is free.
Seems City Slicker featured this a while back.