] Now, here's a quote which casts doubt on the idea that young Mr Darcy ran over to the horse chestnut tree (not five miles away) to gather conkers:

If I remember correctly, Mr. Darcy never says anything about "conkering" in the book or the movie in that scene. My memory runs something like this:

Darcy: I remember running there (Lambton) from Pemeberly almost every day in the horse chestnut season. There was one very fine tree there I recall...

Mrs. Gardiner: On the Green, by the Smithy.

Darcy: Exactly the one.

So, maybe Darcy just liked the tree, and wasn't think of conkering at all.