Possible British Citizenship by double descent?

[gypsy.of.the.sea]

Hi all, I'm trying to get some advice about my possible eligibility to get British Citizenship.

My paternal, UK-born grandfather was deployed to South Africa during WW2 where he met my South African grandmother. My father was born in South Africa on 16 July 1946 and my grandfather was officially de-mobilized from the armed forces on 22 July 1946.

My father lived as a South African and had SA passport etc, but he later (about 10 years ago) got his British passport and is now living in the UK.

I was born in South Africa in 1986.

Is it possible to claim British Citizenship by double descent because of my grandfather's time in the army? Even though I am over 18 and have an SA passport?

If it is possible, how do I go about all this? Is it quite a tricky thing? I am currently in the UK on an ancestral visa so I would be going through the process from here.

Any info would be hugely appreciated!

[Gyfrinachgar]

Is it possible to claim British Citizenship by double descent because of my grandfather's time in the army? Even though I am over 18 and have an SA passport?

No. To apply for citizenship based on Crown service, you must be the one serving. Crown service of grandfathers doesn't matter (see here). There is more on the details of citizenship by decent and otherwise in chapter 20 and on crown service in chapter 18 of the caseworker manual. Since you weren't born to a British citizen and weren't registered as British citizen after naturalisation of your father, I think you have to go the full way, at least I cannot think of a short-cut.