While British citizens have a statutory right to enter the UK they must prove they are British, which Hanne is able to provide as she has her birth certificate with her. She was born in Sussex and has lived all her life in the UK.
Under the current law, if neither parent is British or settled, then a child born in the UK can apply for British citizenship if they have spent the first ten years of their life in the UK
But she is British because her father is. Being born in Britain doesn’t make her British without approved application. She must have applied for the passport because she knew about the risk but took it.
The issue is:
The Home Office recently said British nationals could use an expired passport but acceptance as proof of nationality was at the discretion of the airline.
The airline, Norwegian, rang the British embassy in Copenhagen but they could not help.
The airline doesn’t want to take the risk to fly her back to Denmark. The birth certificate which should name her father should proof to the British immigration officer that she is British.
https://en.wikipedia.org/wiki/Jus_soli
But she is British because her father is. Being born in Britain doesn’t make her British without approved application. She must have applied for the passport because she knew about the risk but took it.
The issue is:
The airline doesn’t want to take the risk to fly her back to Denmark. The birth certificate which should name her father should proof to the British immigration officer that she is British.