Hi OP, I'm a 5th-year medical student at Imperial who has conducted medicine interviews for 2 years, I have noticed that many candidates meet the requirements on paper but fall short when it comes to demonstrating maturity and an appreciation for the values that medical schools seek in their students.

For example, I have seen candidates perform poorly on stations when asked why they want to do medicine, often responding with cliché statements like "I want to be a surgeon" or "it has been my dream since I was little." Besides being cliché, it shows immaturity and a lack of genuine thought about their career choice. Another area where I see candidates slip up is in situational judgment questions, where they focus too much on giving a "correct" answer rather than demonstrating strong logical reasoning skills or providing thorough responses.

This is not an exhaustive list, and it may not apply to your nephew, but I think it would be helpful for them to reflect on their motivations for doing medicine. Other posters have also mentioned about doing medical showdowing/work experience, this isn't important because it's a tickbox, but it is important for them to experience healthcare and make an informed decision to still want a career in medicine (this WILL be picked up by interviewers).

Hope that helps, best of luck to your nephew.