Conversation so far:
Why was reburial necessary?
it was decided that they should be reburied at Leicester Cathedral.
Where were they buried before?
Greyfriars Church in Leicester.
Does they mean the remains of Richard III?
Richard III's body was buried in Greyfriars Church in Leicester.

Question: Why was his body dug up?
Self-contained rewrite: Why was Richard III's body dug up?