Plaque: Herman Wallace
Who is Herman Wallace?
This tile is about 4" square. It has been guerrilla-stuck to the wall just above the white 1911 City of Westminster mile marker, which can be seen to the far right of our photo, taken many years ago, before the tile appeared. Google and you will see that similar tiles have appeared at other locations around London.
Site: Shackleton & Livingstone statues (3 memorials)
SW7, Kensington Gore, Royal Geographic Society
Ornamental Passions's post had good photos of the statues. Apparently cabbies call this "hot and cold corner". The room behind is the lecture hall.