British Dialect or Speech Impediment? Rhotacism

I've heard the Elmer Fudd effect from many British speakers and not just from the BBC's Jonathan Ross - also Terry Jones of the Monty Python troup, Dave Murray of Iron Maiden, Frank Muir on the BBC's game show, 'My Word!, and several other BBC reporters.

Here's a great example:
http://www.chinadaily.com.cn/video/2011-12/14/content_14263204.htm

It would seem more likely that the BBC would legitimize a dialect than they would hire someone with an impediment. But that didn't impede Barbara Walter's career.

This effect is apparently called 'Rhotacism'.

I found a forum with the heading of "http://ask.metafilter.com/67058/Wabbits">Wabbits", which delves into this effect prevalent amongst certain Britains.
http://ask.metafilter.com/67058/Wabbits

The question is whether we are hearing a true dialect, a speech impediment, or perhaps a dialect that developed around someone of influence who had a speech impediment. Certainly the impediment is corrected when it appears at an early age here in the States, as are crooked teeth. So what's the scoop?

No greater homage to the phenomenon than the scene in Monty Python's Life of Brian:
http://www.youtube.com/watch?v=2K8_jgiNqUc



Comments from the Wabbit Weblog:

The wikipedia page for Jonathan Ross refers to "a common dialectal variant of English common in the UK called the labiodental approximate. This pronunciation has increased in usage over the past 30 years and is mainly associated with speakers in the South West of England, although Ross is actually a Londoner."

Welsh people do this quite a bit. I spent a year in Wales, and I never got tired of my coworker's breathey "Wheally, Bill?" when she meant "Really, Bill?"
Terry Jones is the Pythonite who does it, and if you listen closely to Catherine Zeta-Jones, she slips her r's for w's when she's excited. On the Chicago soundtrack, listen for "My sister Vewonica and I..."

There's tons of good examples of this trend. An accessible one is found in the Welsh rap group Goldie Lookin' Chain's "Guns Don't Kill People, Rappers Do." The refrain becomes "wappers do!"

It's totally South Wales, like Cardiff/Newport. And you can hear it in some folks up through Powys, but it fades pretty rapidly. For example, lots of people have the r-to-w in Llandrindod and Builth, but almost no one does in Rhayader. And not many in Brecon do, despite Brecon being further south. Brecon and Rhayader have a relatively high number of native Welsh speakers, where the trilled r prevails.

People from South Wales don't trill the r, but they still have the heavy aspirant quality associated with a Welsh accent. It's a "breathy" r that ends up sounding like a w.