Ooh Claret, I wish you hadn't dug this one up again. It messes with my head every time I look at it
In a nutshell, I have no absolute proof that Olive Nutter's maiden name was Leaver. The only record I've ever found of Olive Leaver was her birth in the Haggate Chapel birth records. No trace anywhere of the birth of the Alice Leaver named on John Nutter's marriage certificate.
I do believe that Alice Leaver and Olive Leaver were the same person and that there is a mistake in the marriage record but you'll have to make up your own mind about this.
My reasoning is based on the following:
1. Olive Nutter and Olive Leaver have the same birth year.
2. They have the same father.
3. There is no record of the birth of Alice Leaver or the death of Alice Nutter - the only reference I can find to her anywhere is the marriage.
4. The marriage was in 1840. By 1841 John is with Olive. It's unlikely that the woman he married in 1840 would already be dead and replaced by then - but I accept it's not impossible.
5. John and Olive's first child has the same name as Olive Leaver's father - Bannister.
6. There are 2 Leaver children (I don't know whose) on the 1841 census and one of them (Abraham) is still with them in 1851. This suggests some realtionship with the Leaver family. (By the way, I've looked at Abraham's marriage record but no father is named. He can't be one of Olive Leaver's siblings as her mother died before Abraham was born).
As I say, you pays your money . . .