Recruitment agencies are normally used to filter out the applicants that are the closest matches for the profile supplied by the employer. The applicant should try and understand the profile of the job and tailor their application cover email and CV web page to the particular job. For senior jobs some recruitment agencies and companies rely on pschometric and other personality and skills tests. These can last for hours. An initial interview with a recruitment agency can be followed by a first and even a second interview with the employer.
First impressions are important.
It is always important to understand who is on any interview panel. They will ask questions about the job but will be trying to discover how you react in different situations. They will try and upset you, to question your knowledge, to see if you can handle stress and abnormal situations. Honesty and good humour is always the best approach. Try to reduce tension but address the question in a focussed and succinct way.