a 2.1 would do as academic requirement. a relevant internship and good recommendations would enhance your profile. King's MPP is mid tier at best and I rarely see people rejected. Some applicants use KCL MPP as back up when they apply for more competitive MPP programmes (UCL, LSE, Oxford, Cam), other competitors are Bristol, Warwick, Edin, Nottingham.
In forums, you read often about people who got admitted to KCL MPP but decided to enroll somewhere else. KCL strongest point is possibly security. KCL's IPE, Development, IR Theory, Governance and analytical methods are mediocre compared to aforementioned peers.