Thanks for replying, Ruskie. I don't know when the original research was done, but I think it was fairly recent - possibly 1950 onwards. There are some family history websites on ancestry including one on the Nuttall family and Thomas Clarkson and his family appear to have been high-profile members of the LDS church. It was thomas' daughter elizabeth who married William Nuttall. I have been in touch with a few people who have contributed to current trees, and they do not have any knowledge of the research done in kingston upon Hull.
Again, I do not know if there is a single source, but I have seen references to an Author called Mavis Moore Smith who wrote a couple of small books and here is what the website
http://www.nuttall.us/about.html has to say about her:
Mavis descends from William Nuttall through Leonard John Nuttall via
Leonard John Nuttall, Jr. She has been active in genealogical research
for more than 40 years having first travelled to England in search of
Nuttall family genealogy in 1960. She has served in family history
services and has actively taught genealogy classes. She works as a
genealogical consultant at the Utah Valley Family History Library at
Brigham Young University in Provo, Utah.
The website also says that the familysearch genealogy was researched by Mavis Moore Smith. Unfortunately, the Nuttall website does not have a contact point for her, and it concentrates on the Nuttall family.
For a while - and there are still some trees out there with a connection - I believed that my ancestors were descended from Thomas' father Joseph. Now that i have more information on my Joseph, i know they are not the same people. But I am pretty sure the families intersect at some point, just because of the place and time and naming patterns. I am interested in finding more about the original Clarkson research because i think it will help me place my Joseph, the father of samuel who is my.... 5 x? great grandfather. at present, I have samuel's baptism as a child of joseph only, nothing about his mother and no marriage that fits. Samuel lived quite close to the Joseph who is Thomas' father in Kingston upon Hull.
I am hoping that someone can point me towards that interesting research on the other clarkson family!