What is the importance of Whitehaven in the novel, The A.B.C. Murders?

Whitehaven is Poirot’s home, where the action of the novel starts, and where Poirot and Hastings keep going back to. The letters all go to Poirot at this address and it is, also, the place where Poirot is able to get some distance and reflect on the case. Poirot solves the murder in Whitehaven, right in his home.