I may have assumed that Bert and Mike's tunes were the same. I only heard Bert sing it a couple of times whereas I heard Mike sing his almost on a weekly basis and my memory's not that good. My tune is definitely based on Mike's. I've never bothered to check if it was a traditional tune, I just fell in love with the tune. But come to think of it it does sound a bit like a minor variant of the thyme tunes.