I obtained details of Ann Walker's marriage to William Carr and on Ann's ancestors from Ancestry use "mrsleonard1" (Linda). Below is her message:

Hello Peter,
My great grandmother was Mary Walker from Upper Poppleton. Although it is a common name, all the Walkers in Poppleton in the 19th centuary were one family and can all be tied together.
As Ann is not a direct ancestor, I’m afraid I don’t have a marriage certificate but if you look on the GROs on Ancestry or FreeReg, you’ll find Ann Walker was married, last quarter 1851, in York vol 23 p853, but she is all alone. William Carr has been mistranscribed as p153 but the original image shows p853.
That in itself is not definitive proof but the 1851 census has William Carr, born Barkston, and Ann Walker, born Poppleton, both living and working on a farm in Saxton, which explains how they met.
Later censuses show that Ann, wife of William Carr was born in Poppleton and by 1901, William Walker, Ann’s brother, was living with Ann Carr, widow and her son William Carr. When Isabella Smith (by then Walker) died in 1873, the informant on the death certificate was Charles Carr, but unfortunately he didn’t say he was her grandson.
As you can see, the evidence is building up. If you ever get the marriage certificate, will you let me know the details, please?
As to Ann’s parents, you can find her baptism on the IGI. The only marriage I have been able to find for a John Walker and Isabella, was the one in Long Marston. The original register gives no details apart from the names of the witnesses. However, in 1861 and 1871, Isabella said she was born in Killinghall and the Ripley baptism register has Isabella Smith, daughter of Simon Smith and Martha Johnson of Spruisty, Killinghall. John and Isabella called their first child John and the next two were Simon and Martha, which proves nothing, but I’d be prepared to put my shirt on this being the right family.
Let me know if you want any more details.
Linda