How do you get the Record Breaker challenge in Batman Arkham Asylum?

I've finished Batman Arkham Asylum and found every challenge except the record breaker. I've been looking through various websites but I still can't find the answer. Does someone know how to obtain this challenge?How do you get the Record Breaker challenge in Batman Arkham Asylum?
Record Breaker



How to Unlock: Collect the Riddler Trophy inside the Warden's Office of the Arkham Mansion (Trophy #25).



Medals



Fall Guy: Batclaw a henchman and pull him off a walkway to take him down.



Over the Ledge: While hanging from a ledge, grab a henchman and pull him off the ledge.



Round the Bend: Use Corner Cover to hide and then take down an approaching henchman.