How would tou prepare for the HireVue

The truth is that at the junior level, the difference in experience or even junior banker across firms is basically 0 due to the randomness of recruiting. You're not a senior, the internal policies of the firm doesn't impact whether or not you can run a deal, because you're no where near that level of doing something like that.

It is therefore incredibly stupid to renege for another BB. It doesn't make any damn sense.

Of course, they won't be happy with you, but there are no consequences. In the end, I would choose the team you have the better connection with

Let me explain my experience of reneging in London. Nothing fucking happens. They’ll just ask for a call or a zoom meeting worst case and you just need to say personal reasons. There’s no legal consequences for reneging — end of the day it’s a fucking work experience program. You don’t want to go gain experience? Fine. Everyone stop with the bullshit that oh it’s stupid to renege.