The marriage is not on the IGI or BVRI, so the next best thing is to check on FreeBMD -
http://www.freebmd.rootsweb.com/cgi/search.pl or go through the images quarter by quarter which can be done free at
http://www.ancestry.co.uk/search/rectype/vital/freebmd/bmd.aspxYou'll then need to purchase the certificate for any likely marriages
Another, and more reliable, way of finding Mary's maiden name is to purchase the birth certificate of one of her children. You can then find the correct marriage in the marriage index. Rebecca's birth was registered in the Dec quarter of 1843 and her baptism is on the IGI - if you then click on the batch number on the Individual Record, put in Prime in Last Name you will get all the Primes baptised in Barley for the period covered by that batch. There is an earlier James Brand Prime in 1842 - I wonder if Brand might be a clue.
There's also an 1832 entry for a son of James and Eleanor - given the age difference between James and Mary I wonder if this might be an earlier marriage for James. There's a death of Eleanor Prime on FreeBMD in the Sept quarter 1839 in Royston reg. district which includes Barley.
I can't find them in 1851**, which would have been helpful, but living in Holywell cum Needingworth was Daniel and Eliza Prime and family, including Abraham 16, who were living in Barley in 1841. Daniel was a blacksmith and there was also an Abraham Prime 71 blacksmith living in Holywell in 1851 (and 1841). If you'd like full details of these I'll run them off. It would not surprise me if Abraham, Daniel and James were connected. I do not believe in coincidences.
I'll carry on looking
Regards
David
** Found the family in Barley in 1851, although James must have been away as he doesn't appear. Do you have details? Probably not.
HO107/1707 folio 409A
High St, Barley
Mary (indexed as May) Prime wife 34 b Needingworth (indexed as Kneedenpworth Hampshire! - no wonder I couldn't find them)
John Prime son 16 ag lab b Barley
Rebekah Prime dau 7 scholar b Barley
Fanny Prime dau 6 scholar b Barley
Mary Ann Prime dau 2 b Barley
Susan Whitmore lodger unmarr 36 dressmaker b Barley
I am beginning to believe that it was a second marriage for James!
Later
Finally found them in 1841
HO107/443/4 folio 34B
Hamlet of N?ewsells, parish of Barkway (2 miles from Barley)
James Prime 30 ag lab
Mary Prime 20
Frederick Prime 8
John Prime 7
Henry Norris 15 ag lab
All born in Herts
So it was a second marriage for John, and it took place between Sept 1839 when Eleanor died, and June 1841, the date of the census.