So there I was, furkling around on Rootsweb and I found a Ruth Culpin who was born in the nearby county of Huntingdon. The daughter of John & Elizabeth, she married William Andrew and emigrated to Australia a couple of years later.
I can find her in the 1851 census, in the workhouse in Huntingdon, recorded as an unmarried farm labourer born in Steeple Gidding (I'll spare you their spelling!); I can find her marriage in 1852; and I can find two children born to a Ruth Culpin in Huntingdon in 1846 and 1851, both of whom died as infants.
But I can't find Ruth's christening, so I can't find her parents.
I can find two Culpins christened in Steeple Gidding: Catherine (1828) and Caroline (1831), both the daughters of John and Elizabeth. I then found these girls in the 1841 census, still in Steeple Gidding, living with the family of William Hospital (that's what it says).
And I'm even more puzzled and confused. Because there is an Elizabeth Aspital in the tree, who married Charles Culpin in St Ives in 1809.
I think the next move (or one of them) is to go and look on Ancestry.com, the worldwide version, which I can access at the library; then I can search the Australian BMDs. The Aussies, bless their little cotton socks, very kindly put the parents' names on the death registrations so, if I can find Ruth Andrew, I may get a clue .....