Barcap is a company of long history, and known for being proud of its culture.
Try to prepare yourself on the following:
1. Research a bit more about Barcap, knowing what's special about Barcap compare to other IB
2. Think more about your own direction and try to find out the alignment with Barclay's culture and value. One of the objectives of Barcap's tele-interview is to find out which vacancy the candidate can fit in best, in term of both your quality and willingness. Knowing where you want to go will help you to give clear signal to them and save you more time to talk about your strength and appreciation of Barcap.
3. Knowledge about investment banking, even if you're just applying position from tech depart.