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Kate Middleton arrives at the West Door of Westminster Abbey in London for her wedding to Britain's Prince William. - 

JEREMY HOBSON: Did you know there's a royal wedding going on this morning? Yup in just under 10 minutes a commoner will walk down the aisle at Westminster Abbey to marry the heir to the British thrown. Now, historically, royal marriages were important for the political and economic future of a country.

So if that were still the case today should Prince William really have married Kate Middleton?

The BBC's Rebecca Singer went to find out.

REBECCA SINGER: If Prince William had stuck to convention, the lady walking down the aisle this morning should have been a foreign Princess or at least from aristocracy. Someone who would bring a strong political alliance with another country, help boost trade or at least acquire new territory.

David Carpenter is Professor of Medieval History at King's College London. He says if Prince William had really wanted to improve the outlook for the U.K. economy, he probably should have married the daughter of a high Chinese communist official.

A huge increase in trade between England and China and possibly Chinese financial support if there was another economic crisis in Britain.

In fact Prince William could have found several examples from English history. A Portuguese Princess whose marriage to Charles II brought the port city of Mumbai under British control. Or a French Queen who owned a large wine making region of France -- and through her marriage to Henry II helped Britain become one of the biggest markets for red wine.

But Carpenter says if Prince William had really wanted to follow in the footsteps of his ancestors -- he should have tried to marry one of President Obama's daughters. Possibly securing the special relationship British people like to think they have with America.

In London, I'm the BBC's Rebecca Singer for Marketplace.