CELTA Course Interview - what to expect?

Hi,

I have my CELTA Course interview coming up, can anyone advise what to expect? I also have to do a 5 minute lesson on a subject area of my choice - how should I approach this? I train colleagues on data protection at work, should I do a session on this or should I teach some English Grammer? What are they looking for? I'm suspecting that there will only be one course place for every 4/5 applicants and I don't want to fail, any advice will be greatly appreciated.

Many thanks

Kevrah