I'll trade you for my infuriating grx2 grandparents not far away from yours. They married 25 years after their first child was born, 7 years after their last - and I can't find a previous marriage for either. She has a rare surname and he has a rare given name, and this all transpired well post-1837, and they were in their very early 20s when the first child was born and together in the 1851 census three years later -- so if a pre-existing marriage was there, I would have found it. Both claimed to be never married when they married at the age of 45. Just conscientious objectors, or lazy, I figure.
Your Rebecca was born 1812-13ish per censuses. By 1841, she could have been the one with the previous marriage still operating as a bar up to 1854, even though she was a decade younger. And especially given the baptisms with mother Maria in the late 1830s.
Keep in mind too that she may have aged slowly. In 1841 she was aged 30, which would ordinarily mean born 1807-1811. And between 1851 and 1861, they both lost a year. So she could have been the mother of James. Even if she was born c1813!
In 1861, Simon and Rebecca had kids born in the last decade.
Gedling Hancock, 1855 Radford
I'd get that certificate to be sure of Rebecca's birth surname.
Yeah, I did in my case, and her birth surname on the child's birth certificate was the one she married under 7 years later.
You might get the same results -- Rebecca was a spinster at the marriage and the surname on the birth certificate is Cutts -- but at least you have some evidence that Simon was previously hitched! What his marriage certificate says about it would be worth knowing.
One thing might be, in both our cases, that the parties had represented themselves as married for so long that it took some precipitating event for them to admit they weren't and do the deed. Could have been death of a previous spouse, or the prospect of death for one of themselves, or that sort of thing.