Actually two things, both represent fine Welsh companies (!) AND both use Nifty Corners for generation of rounded corners on coloured blocks.
I was using niftybefore I saw the S4C site, so perhaps their inspiration came from bochgoch.com (I wish!).
I do like the minimalist clean lines and colourful but unfussy design of the S4C site. Some other TV companies (channel 4) could learn from it…
Have a poke around bochgoch.com and the S4C site and see it in pretty rounding action.