When you say that you got the DOB from Ancestry, is that the record or from a Family tree on Ancestry. ?
It is well known that some family trees are rather fictitious, and some owners grab any records that seem to fit, without sources and pure guesswork.
The only record from Ancestry record set for London is this one....................!?
John Talbot
Gender: Male
Record Type: Christening (Baptism)
Baptism Date: 12 Mar 1769
Baptism Place: St Giles, Cripplegate, City of London, London, England
Father: Edward Talbot. Occ. Taylor.
Mother: Darkis Talbot
Register Type: Parish Register
