Have to agree with brit bus driver:
I remain convinced they are there to hire, not to turn you away.
Having recently spoken to a senior person intimately connected with the BA pilot recruiting setup, it was confirmed that you're at the interview and assessment day because you appear to meet their needs - you 'fit the mould'. It is up to you to prepare, do the homework, and they will see if you still resemble that 'mould' at the end of the process.