Why do you want to leave your current job ?

I was very open with my HR, she actually thanked me for my honesty and said that she wished more people were as straightforward.

I feel my growth here has become stagnant. I've learnt a lot working with great minds here, but right now I'm at a point where I've realised that I've reached my ceiling point here and now to enhance my skills and work on something new, more challenging, I'll need to move out of my comfort zone.