I don't know Barbara Walters but the Wiki for her suggests her impediment is on the pronunciation of 'R' as more like 'W'. The UK equivalent would be Jonathan Ross, I guess. Non-UK readers (and young UKers!) will probably not know Patrick Campbell had the sort of stammer that makes you unable to speak for a second or two. Hence the title of his autobiography p-p-Penguin Patrick Campbell. That was published in 1950; I wonder if it inspired the UK advertisment many years later "If you feel a little p-peckish, p-p-p-pick up a penguin".

Anyway, it's hard to imagine anyone with such a pronounced stammer making it on mainstream TV now.