Open House London
This year Open City presents the 20th Open House London, which takes place on 22 & 23 September (CLICK). Although billed as a festival of architecture, Open House London is our one chance in the year to view art treasures in buildings not normally open to the public. The Guide is now available to order from Open City or you can try your local library for a freebie. Web listings go live sometime today (CLICK). They weren't online when I visited at 11am this morning.
Update: the listings won't go online till Monday.