Among the many other things it brings to the fore, the London gaffe provides a bracing reminder of Romney's relative inexperience. Right-wingers love to talk about Obama's lack of experience, and I wouldn't deny that they have a point. Two years in the Senate wasn't much, and I'd even agree that there have been times when his lack of experience, combined with his aloof nature, have hurt him, and maybe the country here and there.
But what's Romney got? In fact, far fewer years in public office than Obama had--Obama's 10 total years to Romney's four. Obama worked in a state capitol, just like Romney, and then at least he had two years in the Senate.
You can say well, at least Romney's experience was a chief executive, and that's true. But being a governor is not much like being a president. I doubt most recent ex-presidents would argue that their time in Little Rock or Austin or wherever really prepared them for the White House. And of course a gubernatorial term does nothing to prepare one for interactions on the world stage, as we just painfully witnessed.
This is one reason why Romney keeps touting his business experience. There are class and racial presumptions woven into that--that a rich and successful white man with a bold jawline must surely know what he's doing. But he keeps demonstrating that he doesn't. Maybe, despite the fact that he's from central casting, he just isn't ready for prime time. He's the 98-pound-weakling dressed as Charles Atlas.