His billions come from the family's ownership of 300 acres of Mayfair and Belgravia in London. But it wasn't William who gave them to the family - he gave them a chunk of Cheshire.
Rather, it used to be the marshy farmland that made up the manor of Edbury. The owner of that left it to a nephew, a clerk, who died in the great plague of 1665. In 1677, his widow sold the sole heir, their 12 year old daughter, Mary Davies, in marriage to the highest bidder. That was the 21 year old Thomas Grosvenor, who paid £5,000.
In terms of business advice, 'Buy a 12-year old heiress' doesn't quite have the same ring, does it?
This entry was originally posted at http://lovingboth.dreamwidth.org/562857.html, because despite having a permanent account, I have had enough of LJ's current owners trying to be evil. Please comment there using OpenID - have and if you have an LJ account, you can use it for your OpenID account. Or just join Dreamwidth! It only took a couple of minutes to copy all my entries here to there.