This one, for Bovril, I found in Brixton, in Windrush Square (a newly landscaped public square which opened in 2010). Bovril, for those unfamiliar with it, is a thick, salty meat extract created in the 1870s.
If you look closely, there's the outline of another advert below. This was an advert for Butlins Holiday camps, but it's now so faded you can hardly make it out. It'd be nice if they decided to repaint these ones, or maybe history should eventually fade away. What do you think? - Lucy