What constitutes a credible Yes vote on March 3rd?

Not sure whether I offered a 'hostage to fortune' on the Politics Show today. The subject under discussion was the referendum concerning law making powers for the National Assembly on March 3rd. What turnout is needed to accord credibility to the result. I suggested that I hope 50% of the Welsh electorate will vote - though I have to admit I do not think this will happen. I added that if the turnout was not more than 35% of the electorate, credibility would be an issue. What do you think?

Two points to note. Churchill is supposed to have said something like 'one is a majority' - implying that nothing else matters. And secondly, even if 50% vote, its unlikely in my opinion that 30% of the Welsh electorate will have voted Yes - challenging credibility in some eyes, who believe there should be a threshold of Welsh voters voting Yes of 40%.

I did note that none of the other guests risked putting a figure on it.