SOAS university has a small gallery space dedicated to exhibitions about Asia, Africa and the Middle East. There's a small but beautiful Japanese zen garden on the rooftop (currently closed for refurbishment)
A traditional pie, mash and liquor shop in south west London that is run by the latest generation of the Harrington family who opened it in 1908. It looks like it hasn't changed since the day it first opened but it's a place with absolutely no pretentiousness to it at all, this is unapologetically working class and down to earth. If you want an overpriced cappuccino and wi-fi there's a Cafe Nerro down the road but if you want fantastic traditional London food you won't find anywhere better in the city. They even do pie and mash to take-away. I just wish it wasn't closed on Sundays.
A treasure trove in the The City of London. The Archive of London. Strongrooms hold kilometres of shelving; boxes of matter that has somehow been catalogued and categorised in a traceable manner by the public, for academic, genealogical and other research. This beautiful book is from a box on Epping Forest. On the same visit, I looked through photographs of Blitz singsongs in Bethnal Green Underground station, 1980s anti-Thatcher / pro-GLC gig posters and paper concertina optical models of the Crystal Palace.
Also the Queens back garden, these beautiful grounds are great for a Sunday stroll to see the pelicans or to feed the squirrels. Duck Island Cottage is worth a look too, a idyllic little cottage situated in the grounds which was specially built as the bird keepers home.