Why are the Brownriggs and their neighbors angry with Sir Philip Morton?

The Brownriggs and their neighbors are angry at Sir Philip because he came and put a wall around their land... claiming it all belonged to him and raised their rents.

Down in the valley, by the river, the meadows have been common land since time immemorial. I don’t say they belong to nobody — they belong to us , Brownriggs and Bells and the rest of the families who’ve farmed Lonsdale all these hundreds of years. And heaven help the man who puts a stone wall round them and calls them his — even if he has money and men in livery and a “Sir” in front of his name.

That’s what Sir Philip did that summer.