article_snippet.sent: Scroll down for video .
article_snippet.sent: One onlooker, who asked not to be named, said: 'I've seen a couple of guys on different parts of the roof throughout this morning. '
article_snippet.sent: A man was walking across the roof of the arch this afternoon wearing a black sleeveless hoodie with the hood pulled up and a black scarf across A man face.
article_snippet.sent: No Russel Brand on hand here....