Acton alleges that William the Conqueror invaded England in 1066. This may well be true, but he does not give any footnote for it and I have been unable to make any independent assessment of his evidence. It is true that some other historians such as Smith (footnote) and Jones (footnote) mention the same thing, but it may be significant that they were writing later than Acton, and were perhaps uncritically repeating what Acton had said. We need to take into account the possibility that Acton was biased. Perhaps his family was of partly Norman descent. At all events, we should not accept claims like this without better evidence than he has given us. [Footnote can be imagined.] I.W. Mabbett, Writing History Essays: A Student’s Guide (Palgrave Macmillan, 2006), 45.