The excellent website 'London Remembers' by chance draws my attention to two unidentified memorials in London, of which the above is one. This is a painting of a girl of unknown age which is placed exactly between the semi-detached houses at 17 to 19 Glenilla Road in NW3, but no one seems to know why. My guess is probably wrong, but I wouldn't be surprised if this concerns the death of a much-loved adolescent. The date of the mural is obviously 20th century, but that, I believe, is all that is known for certain.
The second memorial is a small plaque that simply says 'Anna Fauguet 1878–1939'. This is at 4 Brayfield Terrace, Islington, and again no one knows anything about this person, and the only online references to Anna Fauguet refer to the original post by 'London Remembers'. They suggest that the plaque looks 'continental', and certainly it seems French to me, as suggested by Anna Fauguet's surname. Perhaps we'll never know.