Hello,
I have not come across a Jack in my tree,my great Grandfather was born in Little Horton in Bradford and there were a lot of Deightons in that area,and as the library assistant in Bradford said to me when there is a cluster of families like that they have found from research that they are all mostly related.My G-Grandfather was a James,married to a Emma Whitehead,I come from LEEDS.

Regards,

Les Deighton.