Hello All
I've been following this thread with interest for a while now (better than the soaps onTV) and couldn't resist the temptation to chip in. From 1858 onwards all divorces and annullments are listed in J77 at the National Archives, which you can search on their website for free, and there is no divorce/annullment for Joseph and Emily Clarkson.
I discovered this after researching a bigamist in my own family, but in his case he didn't go as far as Scotland, just Sunderland. Back in those days, who would know if a stranger who turned up in town was married or not, and how would you ever find out for sure unless the previous spouse showed up and made a fuss? The formality of a divorce was only for the rich and well-connected. In my gt-grandad's brother's case he said he was a batchelor on the second wedding certificate even though I can find his first wife, also remarried with children, still alive on the census. She remarried before he did and I can't say I blame her, as he served two months in prison for beating up her and her mother; she had left him after two months of marriage after he threatened to murder her!
All your evidence seems to point to Joseph Clarkson being a bigamist and a rogue, but of course he's not the only guilty party. I'm sure Fanny must have been aware of the consequences of a fling with her sister's brand new husband before she embarked on it, not to mention the effect it would have on her sister.
Best wishes
Liz