In my copy of this book, I put quotation marks around the chapter title, specifically around the words "No One".  To the Dursleys, the magical world that these letters are from are "no one", because they despise what they stand for. Their use of "no one" is disparaging. Harry thinks the letters are from "no one" because he is completely ignorant of the magical world, and is unable to find out who they are from.

Two details to the non-British. The address of 4 Privet Drive is revealed in this chapter to be in "Little Whinging, Surrey". "Whinging" is a synonym in UK English for whining (as in complaining). Surrey is a posh, upper-middle class county to the south-west of London. This very much signals the wealth, class and suburban lifestyle of the Durselys.

The letter, which is commonly misremembered to be written in black ink with a red seal, is actually written in emerald-green ink with a purple seal, though any true Hogwarts student would know this. This further corroborates what I have mentioned about emerald-green and purple being uniquely "magical" colours.  They are the robe colours of McGonagall and Dumbledore respectively in chapter one, and the colour of the outfits worn by the strangers (wizards) who greet Harry on the streets in Chapter Two as well.

One question I asked myself reading this chapter was: "Why are the Dursleys so against Harry going to Hogwarts? Shouldn't they love the idea of being rid of him for most of the year?". After pondering this for a while, I came to the conclusion that their fear of the abnormal (magic) must overpower any hatred they hold for Harry.

Whilst not featured in the film adaptation, the book details that the first place the Dursleys attempt to escape from the letters is the Railview Hotel in Cokeworth. With a name like "Railview" and "Cokeworth" (similar to Dickens' "Coketown"), we can tell that this is an industrial, likely lower class area than Little Whinging, and is said (though not in the text) to be in the Midlands. One thing that a second time reader might notice is that Cokeworth is actually the town in which Spinner's End, Snape's childhood home, is located. Petunia (and Lily) would have lived close to or in this town growing up. It seems rather odd that Petunia would let Vernon take the family to this town, when it has magical associations for her, but perhaps they thought it was innocuous enough.

In summary

• The meaning of "No One"
  


• What does "Little Whinging, Surrey" mean?


• The colours of the Hogwarts letter


• Why are the Dursleys so against Harry going to Hogwarts?


• The significance of Cokeworth