I was told that this would be an informal chat and would not require any preparation. Obviously I researched the company and got some advice from a friend who regularly interviews people for similar roles. When I turned up the interview consisted of very formal competency based questions which I've always been told about beforehand for other companies. When I asked the interviewer at the end about the interview process, next step etc she told me she had so far interviewed 20 people and still had a couple more to go!! She was clearly very inexperienced and was getting little support, she was only taking 2 of the 20+ through to second interview. I would not have wasted my time if I had realised this was the process, based on how long my interview took it must have taken her at least 6 full days of first round interviews for a £25-30k job!!