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.
Why was his body dug up?
Following the discoveries of Richard's remains.
How were the remains discovered?
CANNOTANSWER.
Who decided to rebury the remains?
CANNOTANSWER.
Was there a ceremony when the reburial happened?
at a religious re-burial service.

Question: What clergyperson officiated?
Self-contained rewrite: What clergyperson officiated Richard III's reburial at Leicester Cathedral?