Analyst play politics to hinder my recruitment

I'm based in London and currently doing a top-tier Master in Finance (think LBS or Oxbridge level). I’ve also completed three relevant M&A internships. I’m originally from the Balkans, where the finance network is quite small-people across BBs tend to know each other. 

There’s one person from my undergrad who wasn’t particularly fond of me, as we had some disagreements in a university society. They’ve now joined a BB and are quite close with others from our region.

I’m a bit worried they might speak negatively about me during recruitment, which could affect my chances, not just at their bank but potentially elsewhere too. 

How much influence can an analyst actually have in situations like this?