Jesus. This one was a right bugger to photograph. Twenty sodding paces long, and stitched together from 17 images. You have to imagine the four rows arranged end to end in one long row if you want to read it.
You can find the writing down Shelton Street in Covent Garden. (There's also a bonus graffito from Monkeyboy above it.) Apparently, these are the lyrics to a song by Hair, and have been here for some time.
Well, it's certainly a little bit more involved than spraying 'Tox' on a wall.