How to find birth certificate of adopted person

[LizzieL]

The point I am trying to make is that this post is about a specific person abandoned as a baby. If the mother is so desperate to get rid of her child and ensure no connection to herself, she is hardly going to register the birth before dumping it. Any subsequent registration of the foundling by the appropriate authorities will only have an approximation of the birth date and no information on the birth parents.

We all know what should happen as regards birth registration in 1924 and that although formal adoption wasn't introduced until a few years later, some children were retrospectively adopted. 
OP has stated

A recent DNA test showed my husband as half italian.  We linked to a family member so have the surname of the family in question.  His mother was adopted but doesn't appear to have a birth certificate in her adopted name.  The added issue is that her birth year was 1924 so before any adoption registrations were documented.  Even worse is that anyone who would know anything has now passed.  We assume that there must be a birth certificate with her biological name on it logged somewhere, but we don't know what that name would be - we only know the date of birth and area of birth. She doesn't appear to be registered under the name of the italian person.   Rumour also has it that she was left on the doorstep of a church but we don't know whether that is true or not.  We have an idea of the potential father but suspect this was an illicit encounter as his wife had a baby in the same year but the birth dates do not match so wasn't a potential twin.   Does anyone know whether we are able to identify a birth certificate at all or is this an impossible task. 

I am failing to understand why they should make this assumption given that the lady in question was a foundling

[Glen in Tinsel Kni]

Nothing to prevent a mother registering child and providing whatever details she wished to but it makes little difference. Anything can be written on a certificate but that doesn't mean it is correct, the DNA wins every time.  My grandmother registered 16 children though 4 were abandoned between 1918 and 1928 within a month of the registrations taking place. Some of her descendants refuse to accept their DNA results as they contradict the paper trail, a few 'we're not related' comments have been made over the years, some via comments in public trees,  to people they share 350-400cM with, I sometimes wonder how different it would all be if the certs didn't exist.

[wivenhoe]

" His mother was adopted"

What is your source for this information?

[haliared]

If from England and Wales then this link should help you know where to go next:

https://www.gov.uk/adoption-records