This weekend, 18+19th September, many usually closed doors will be opened to the public for a free snoop inside. And there are walks, tours and cycle rides too.
Lots of gems. Two days only.
Most of the big attractions such as Centre Point and Trellick Tower aren't even worth showing up to now as they were only available to see by booking in advance.
And please be aware that a huge chunk of the properties on the list are actually open all year round, so save those for another day and instead make use of the opportunity to go and sniff around other people's architectified* homes.
Check the official site for more details.
*my own word