Now if I could just track down the death of Rebecca Dransfield! It has to occur somewhere between about June 1869 and October 1874!
Well she was alive in the 1871 census.
As I previously advised, don't assume she died before Thomas married in 1874.
It's possible the marriage to Rebecca was not consummated, and they both agreed to move on. Rebecca may have married again too.
Looking at the 1874 marriage certificate, does Thomas call himself a widower?