In the Civil Service, you are frequently interviewed by panels made up of your immediate managers (in terms of grade) or people you already have working relationships with. In most departments, an average length of employment will mean you encounter, and are known to, most managers and senior managers.
An update. I survived the sift and after speaking to a senior CS (from another department) about this, I expressed my concerns to the Civil Service Commissioners on some detail. I've been advised that the composition of the interview panel had now changed and would be provided details in due course. CSC were very good about and mentioned that this is not uncommon.