I had the same interview with Westjet (actually 2 of them). Their interviews are "behavioural interviews" based on past experiences with work and people.
Tell us a time when you strongly dissagreed with your team, but had to agree in the end, just because the majority did. Why did you do it?
Tell us one time in your past experience when you used humor to neutralize a tense situation.
Be prepared for these types of questions. First of all, look neat, smile and don't make stuff up. I've been told by some employee at Westjet that it's ok to even bring notes to your interview, to help you remember better.
I'm not sure about UK, but hopefully it's the same.
Let me know how it went
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