Weihan was a real joy to be around during the PhD- always happy and smiling, and raising everyone’s spirits with his positive attitude. Any PhD has its ups and downs, and different people cope with it in a variety of ways. What was striking about Weihan was not only that he seemed to deal with the stresses of the programme well, but that his positive attitude was so evident and resilient. It was a pleasure and a privilege to have known him and to be able to call him my friend. I was greatly saddened to hear of his passing, and I hope his family know just how much those who were fortunate enough to meet him valued his friendship.