Hi Ruskie,
The entry in the bapt. register reads;
3-9-1876 Sarah Buckell d/o Henry John and Harriet Eliza of Didcot -Christened “Elderfield” .
Elderfield being Henry John's mother's maiden name as she was single at the time - she was Sophia Elderfield, married Thomas Buckell (died 1861) and remarried Anthony Palmer in 1880.
Harriet Eliza Woodley was, (as far as I know) single when she married Henry in 1873
I have Henry John Buckell in most of the censuses; 1851,81,91,& 1911 all Harwell, Berks
Alan