Morgan,
The information I posted about Annie and John Williams was gleaned from my mother, Eira Kerr (nee Williams), in an in depth conversation around 2000 and I believe her memory would have been fairly accurate at that time. However, memories play tricks and did I record it correctly at the time? I think so because I took, what the lawyers call "contemporaneous notes"! From what you say about Edward Jenkins, founding the Clayton Tinplate Works in 1883 after he had purchased the Ffoesyrefail Works (and renamed it Clayton) and in 1885 and John Williams moving from Abertillery to manage the works, it could be that the Williams line obtained the interest in the business through both marriage and employment. Incidentally, my middle name is Arthur after my grandfather but my brother's is "Clayton" after the works we believe.