I would like to know if one can use a great grandparent's birth certificate to get an Ancestry visa to the UK?
I am planning to move there ASAP and would love to get all the details before making a drastic mistake.
I applied and received an Ancestry visa for the UK in 2009.
My understanding is that you have to show direct heritage, and require either a parent or grand-parent to be British.
Having to go further back - eg great-grandparents is not valid - the link must be more recent than that.
So if you're asking because you don't have British grandparents or parents, then no, you're not eligible.
However, if you're asking because you don't have birth certificates for grandparents and happen to have older ones, then note that you can use various online sources for birth, death and marriage certificates. I used one to get a legal copy of my grandmother's birth certificate, and that went very smoothly - it just took time.