My descent is through Thomas Linnett, son of John and Ann Spriggs and his son son also Thomas. I haven't really looked at the Mawbys beyond Robert.
Thomas Linnett did see the inside of a gaol as a young man. He must have been working as an indentured labourer and:
"Thomas Linnett, farm servant, was charged by his master, Mr Webb of Easenhall, with absconding from his service. Prosecutor said that Linnett had pursued a very dissolute course of life for some time past and he absented himself for some time, bringing with him on his return, a young woman of bad character. Sentenced to one month's imprisonment, with hard labour' Northampton Mercury December 1856. I don't know if Betsy Salisbury (my gg grandmother) was the woman of bad character but she had a child Emily baptised in October 1857 who seems to become Emily Linnett after their marriage in early 1858.