BBC documents the roots of its Global Visual Language 2.0:

About 2 years ago, after printing out the site onto what has now become jokingly known as the ‘Wall of Shame’ we decided to embark on an ambitious project, called Global Visual Language 2.0, with the aim of unifying the visual and interaction design of bbc.co.uk and the mobile website.

I highly recommend actually downloading the guide — it’s a truly remarkable study in visual design.