I've seen these claims (in much more detailed form that the Guardian link lays out, even the link it offers to one of its own articles to back up the claim).

I'd really like to see some differentiation between:

  * a disproportionate number of people of Norman descent remain some of the wealthiest landowners in England

and

  * a disproportion number of the wealthiest landowners in England are of Norman descent

Since these are quite different claims.