0
There are various main characters, recurring characters, occassional characters and so a round number is often difficult to confirm.
See the related link for a list of these characters.
10
They were called:
All of these characters have left Eastenders.
Kat Slater and Alfie!
Christian's last name is Clarke http://www.bbc.co.uk/eastenders/characters/christian-clarke.shtml
^^^
Check there (: