in all other cases, an application for registration of the child as a british citizen must be made before the child is 18. usually this is granted provided the secretary of state accepts the adoption is "bona fide" and the child would have been a british citizen if the natural child of the adopters. usually the adoption must have taken place under the law of a 'designated country' (most developed nations along with some others are 'designated' for this purpose) and be recognised in the uk. this is the standard method for children adopted by british citizens permanently resident overseas to acquire british citizenship.