I always thought it was a little unfair that eldest son would inherit everything and the second or third, or daughter would inherit very little. But now I see, historically speaking, this has been incredibly important in sustaining the architectural heritage of Great Britain. In this way estates were passed down whole, not broken up into pieces and given to differently family members. It also meant that the family's wealth stayed connected to the property, meaning the money to keep up these estates stayed with the estate. During the early part of the 20th century, some of the English families were having trouble keeping up their estates. One solution was to import rich heiresses from the US, where primogeniture was not practiced, and where women could inherit fortunes. Thus theses large manor houses got an infusion of money and were able to stay whole.
Blenheim Palace, all of the photos above, is one of the largest examples of a palace that is still lived in by the owners, the Duke of Marlborough. It was built in 1705 and 1724, it was designed by John Vanbrugh. In the 1890s, the 9th Duke of Marlborough, facing bankruptcy, married Consuelo Vanderbilt for much needed money to keep the estate solvent.