This was potentially the longest time I have ever sat and answered question after question. In total, the questions should last about an hour, but if you're chatty or your interviewer is chatty it will definitely last longer. It is a one-on-one interview, and the interviewer has a set of questions they are given to ask you, everyone is asked the same set of questions. They are relatively impersonal and don't ask directly about your previous work experience, but they are meant for you to draw upon previous experience and apply to the current position applying for.