Tell me, dear reader, what you would do in this situation.
Imagine, if you will, that you are walking down the canalside for your lunchtime stroll when you spot someone walking toward you. This person is wearing a shirt, black trousers and shoes and is probably an office worker in the local area. You'd normally pass them without a second glance but, in this case, the person in question is eating a six inch wrap from a paper bag with every sign of enjoyment while some kind of white sauce drips out the bottom all over his coat, his black trousers and his shoes. He seems oblivious.
a) Stop him and let him know that he is dripping dodgy looking white stuff all over his office clothes.
b) Just let him go about his merry way, perhaps giving him a slightly odd look as you pass
Apparently the residents of Islington favour option B. I must have looked, to use the vernacular, right fucking special; walking down Regents canal holding a large paper bag and covered in tahini. I think I got the worst of it off, and the people in my office are used to me being a scruff so probably no damage done, but it was a bit embarassing.
Anyway, on the way back I saw a Grey Heron on a narrow boat. Score.