As I understand it, for you to qualify for Ancestry Visa, you basically need to prove that your parent was a british citizen
by descent. This doesn't entitle you to citizenship, but does entitle you to Ancestry visa.
So, I think the best way to figure out if you are eligible is to determine if your parent could derive citizenship from your grandmother, which would only be if your grandmother was considered a british citizen
otherwise than by descent. Since she wasn't born in UK, the answer would normally be 'no', as her citizenship would only be
by descent and not transmissable to your parent. But, perhaps your greatgrandfather's crown service got your grandmother 'normal' british citizenship, that is, citizenship
otherwise that by descent. If it did, then she would pass her citizenship to your parent
by descent, and you would be eligible for Ancestry visa.
-- Sat Dec 05, 2009 8:44 pm --
Consulting the following link:
http://www.ukba.homeoffice.gov.uk/sitec ... chapter20/Would seem to indicate that if her father was in crown service, her citizenship is NOT considered by descent, and thus she did indeed have citizenship transmissable to her children -- just as if she were born in
UK [the only caveat here is that women could not always pass citizenship in 20th century] --, and you would be eligible for visa.
based on this I'd be giving it a shot.