As I recall Bangladesh said they didn't want her and wouldn't give her a passport. She was born here so is British by birth, but I think the British government were working on the lines of dual nationality, which, I believe, she could have claimed were she to have reached her majority, she could also have rejected her Bangladeshi entitlement.
Himself was born in London but had an Italian born father, he could have claimed dual nationality but rejected the Italian part saying that he was born in Britain and British he remained to his las breath.