Also, why assume Henry VIII? Henry I reigned in the 12th C, whitehall has been a centre of goverment since about then.

There is no record of a Lord (or earl etc) Arlen in Burkes Peerage, and the 1901 UK cencus has no Arlens at all. The name, has therefore suffered from the folk process.

Going to obvious mishearings does not help, as there are too many options. The nearest is probably the earls of Arden, who have held titles from Saxon times. Not a lot of good....

So neither the King nor the Lord can pin it down. We tried to pin the place down a while back, and that didn't get to a proper answer either. Can't find that thread now. How ironic...