The pavement signs of Borough

Here are two examples of what were originally intended to be informative signs embedded into manhole covers on and around Borough High street.

But alas, as you can see, some of the letters have magically lifted off or just flown away.
I have yet to find one that doesn't have some letters missing so I will make a fairly educated guess that some mischievous folk are having a whale of a time prising off individual letters to hilarious effect.
Ooh my sides have split.