I had a telephone interview with the recruitment agency and then Barclays. I then had to go meet them face to face for a role play interview. It lasted about 45 minutes. They gave me 4 different (fictional) customers information, which I had 15minutes to prepare to serve them as a cashier in the bank. After the 15 mins the interviewers come back in and pretend to be the customers, posing questions at you and you have to try and sell or refer them to other sales people as much as possible.
Things to look out for when prepping are: out of date cheques, working out new bank balance, possible moods the customer might be in, if you've heard them say they are going on holiday then you can suggest holiday insurance and banking abroad, etc etc.