First, the resume/cover letter/transcript application process gains you an invitation to the open day. Based on that, you're also invited to interview for either or both of the paralegal program and/or the graduate program. The paralegal interview process consisted of one interview, and then one day work a week (plus more as mutually agreed) for six months. The graduate interview process consisted of 2 interviews, and the paralegals were 'automatically' put through to the second round.
There were no pre-planned 'behavioural/situational' questions. Questions were based on your resume, experience at the firm, etc.
Research the firm, have some questions you're genuinely interested in asking.