Rules for acquiring British citizenship by descent depend on when the person was born. ====From 1983==== A child born outside the UK on or after 1 January 1983 automatically acquires British citizenship ''by descent'' if either parent is a British citizen'' otherwise than by descent'' at the time of the birth. * At least one parent must be British ''otherwise than by descent''. * As a general rule, an unmarried father cannot pass on British citizenship automatically in the case of a child born before 1 July 2006. If the parents marry subsequent to the birth the child normally becomes a British citizen at that point if ''legitimated'' by the marriage and the father was eligible to pass on British citizenship.