For some reason, I don't particularly object to graffiti when it's old. I suppose the dates could be faked, but I can readily see a '1907' and '1913' (I wonder whether those visitors survived the First World War), and I think there's an '1857' to the right of the prominent 'IG' near the middle of the image. The Roman numerals are 'merely' 1958, of course.
Some of the older inscriptions are well-executed, too; the 'Metcalfe' is distinct, and probably fairly recent (1958?), but constructed of crude straight lines. Compare that to the clean curves of the 'John Faraday' at the lower right.