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By the Nationality, Immigration and Asylum Act 2002 Section 162(5), Section 47 of the BNA continues to apply for those born before 1st July 2006. Moreover, the parents married before Section 47 'ceased to have effect'. The question is whether the OP's parents marriage legitimated him, and this depends on his father's domicile at the time of marriage. If his father has a foreign domicile birth when the OP was born, it's also conceivable that the OP counts as being born legitimate.
His being domiciled in the UK in 1997 does not help you - it makes you born illegitimate. Where was he domiciled when your parents married? If his permanent home was still in the UK, then you are a British citizen and eligible for a British passport. If his permanent home was elsewhere, it gets complicated.